Fix bug for displaying all controllers (ros-controls#1259)

Author: fmrico

rqt_joint_trajectory_controller/rqt_joint_trajectory_controller/joint_trajectory_controller.py

@@ -238,8 +238,11 @@ def _update_jtc_list(self):
         # for _all_ their joints
         running_jtc = self._running_jtc_info()
         if running_jtc and not self._robot_joint_limits:
+            self._robot_joint_limits = {}
             for jtc_info in running_jtc:
-                self._robot_joint_limits = get_joint_limits(self._node, _jtc_joint_names(jtc_info))
+                self._robot_joint_limits.update(
+                    get_joint_limits(self._node, _jtc_joint_names(jtc_info))
+                )
         valid_jtc = []
         if self._robot_joint_limits:
             for jtc_info in running_jtc: