[RFC][LocalSession] Fix workspace type

Summary: I was reading/looking into how LocalSession works and realized that the workspace type being passed around was the bound function on TaskGroup instead of the actual type. This meant that all workspaces for localsession would always be global, because they'd never match the private workspace type.

Test Plan: <not sure, could use some suggestions>

Reviewed By: cryptopic

Differential Revision: D24458428

fbshipit-source-id: 0f87874babe9c1ddff25b5363b443f9ca37e03c1

Author: kunalb

caffe2/python/session.py

@@ -192,7 +192,7 @@ def _compile_task_group(cls, task_group, setup_net_list=None):
             task = task_group.to_task()
         plan = core.Plan('task_group_plan')
         plan.AddStep(task.get_step())
-        return (plan, task.output_list(), task.workspace_type)
+        return (plan, task.output_list(), task.workspace_type())
 
     def _run_compiled(self, compiled):
         plan, output_list, workspace_type = compiled