[MOAB-dev] Should get_parent_meshsets and friends return MB_SUCCESS when passing in the root set?

[James Porter]

Currently, functions like get_parent_meshsets simply return MB_SUCCESS
when the root set it passed in. Should we return an error in these
cases? We have to return an error for iMesh, but to fix this, I can
either check in iMesh or check in MOAB. If there's no reason MOAB needs
to be able to call these functions on the root set, I'll just put the
checks in there for consistency.

- Jim