mypy flake8 issues

[christophfroehlich]

Describe the bug
Since ros2/rosidl_python#206

 - control_msgs.flake8_rosidl_generated_py F811 (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py:1910:1)
  <<< failure message
    redefinition of unused 'GripperCommand' from line 22:
    class GripperCommand(metaclass=Metaclass_GripperCommand):
  >>>
- control_msgs.flake8_rosidl_generated_py F811 (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py:1731:1)
  <<< failure message
    redefinition of unused 'JointTrajectory' from line 18:
    class JointTrajectory(metaclass=Metaclass_JointTrajectory):
  >>>
build/control_msgs/test_results/control_msgs/mypy_rosidl_generated_py.xunit.xml: 22 tests, 0 errors, 22 failures, 0 skipped
- control_msgs.mypy_rosidl_generated_py note (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py)
  <<< failure message
    In member "__import_type_support__" of class "Metaclass_JointTrajectory_SendGoal_Request":
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py:439:16)
  <<< failure message
    "type[JointTrajectory]" has no attribute "Goal"  [attr-defined]:439:16
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py:440:17)
  <<< failure message
    "type[JointTrajectory]" has no attribute "Goal"  [attr-defined]:440:17
  >>>
- control_msgs.mypy_rosidl_generated_py note (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py)
  <<< failure message
    In member "__import_type_support__" of class "Metaclass_JointTrajectory_GetResult_Response":
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py:1162:16)
  <<< failure message
    "type[JointTrajectory]" has no attribute "Result"  [attr-defined]:1162:16
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py:1163:17)
  <<< failure message
    "type[JointTrajectory]" has no attribute "Result"  [attr-defined]:1163:17
  >>>
- control_msgs.mypy_rosidl_generated_py note (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py)
  <<< failure message
    In member "__import_type_support__" of class "Metaclass_JointTrajectory_FeedbackMessage":
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py:1574:16)
  <<< failure message
    "type[JointTrajectory]" has no attribute "Feedback"  [attr-defined]:1574:16
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py:1575:17)
  <<< failure message
    "type[JointTrajectory]" has no attribute "Feedback"  [attr-defined]:1575:17
  >>>
- control_msgs.mypy_rosidl_generated_py note (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py)
  <<< failure message
    At top level:
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_joint_trajectory.py:1731:1)
  <<< failure message
    Name "JointTrajectory" already defined (possibly by an import)  [no-redef]:1731:1
  >>>
- control_msgs.mypy_rosidl_generated_py note (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py)
  <<< failure message
    In member "__import_type_support__" of class "Metaclass_GripperCommand_SendGoal_Request":
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py:618:16)
  <<< failure message
    "type[GripperCommand]" has no attribute "Goal"  [attr-defined]:618:16
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py:619:17)
  <<< failure message
    "type[GripperCommand]" has no attribute "Goal"  [attr-defined]:619:17
  >>>
- control_msgs.mypy_rosidl_generated_py note (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py)
  <<< failure message
    In member "__import_type_support__" of class "Metaclass_GripperCommand_GetResult_Response":
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py:1341:16)
  <<< failure message
    "type[GripperCommand]" has no attribute "Result"  [attr-defined]:1341:16
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py:1342:17)
  <<< failure message
    "type[GripperCommand]" has no attribute "Result"  [attr-defined]:1342:17
  >>>
- control_msgs.mypy_rosidl_generated_py note (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py)
  <<< failure message
    In member "__import_type_support__" of class "Metaclass_GripperCommand_FeedbackMessage":
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py:1753:16)
  <<< failure message
    "type[GripperCommand]" has no attribute "Feedback"  [attr-defined]:1753:16
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py:1754:17)
  <<< failure message
    "type[GripperCommand]" has no attribute "Feedback"  [attr-defined]:1754:17
  >>>
- control_msgs.mypy_rosidl_generated_py note (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py)
  <<< failure message
    At top level:
  >>>
- control_msgs.mypy_rosidl_generated_py error (/home/runner/work/control_msgs/control_msgs/.work/target_ws/build/control_msgs/rosidl_generator_py/control_msgs/action/_gripper_command.py:1910:1)
  <<< failure message
    Name "GripperCommand" already defined (possibly by an import)  [no-redef]:1910:1
  >>>

To Reproduce
#236