glusterfs: Modify interface methods

- Modify interface methods to comply with changes to the share manager.
  The changes were in the following commit,
https://github.com/stackforge/manila/commit/4c8a658d95a4ffd1c01b9b959ab46f8eccc9d26f

Change-Id: I6fde3e6d351f18878dc55fb3535f1dd0b811c352
Merge "glusterfs: Modify interface methods"