Movegroup pushScene mismatch between movegoup and robowflex scenes for Fetch

Fetch in the robowflex planning scene has "world" frame and "base_joint" for integrating odometry. The movegroup we use to execute trajectories on the real robot does not have these frames.

This mismatch causes problems if you want to [push a local robowflex scene to the movegroup scene](https://github.com/KavrakiLab/robowflex/blob/master/robowflex_movegroup/src/services.cpp#L182). For example, the header of a collision object has the field **frame**, which would typically be "world" in robowflex scene, and "base_link" in movegroup scene.

The fix to this would be to programmatically modify the **frame** in the message. We need to see if there is any other fix to do.

Note: This problem does not affect executing an arm trajectory on move group.