set the action when override_method regardless of its None-ness

rest_framework/request.py

@@ -48,7 +48,6 @@ class override_method(object):
 
     def __enter__(self):
         self.view.request = clone_request(self.request, self.method)
-        if self.action is not None:
         # For viewsets we also set the `.action` attribute.
         action_map = getattr(self.view, 'action_map', {})
         self.view.action = action_map.get(self.method.lower())
@@ -56,7 +55,6 @@ class override_method(object):
 
     def __exit__(self, *args, **kwarg):
         self.view.request = self.request
-        if self.action is not None:
         self.view.action = self.action