Remove return stmt of add,save and remove method

Remove the add and save method's return statement in the
ImageMemberRepo class, as the same as ImageRepo class.  Also
modify authorization.py and policy.py and the related unittest.

Closes-Bug: #1254210

Change-Id: I472cd15af8648beea10abc595e905618091f3dab
Remove unused imports in glance

There are some unused import in glance, such as 'import domain' in v2.image_data.py.

Change-Id: I9c3f06bfde4dbf130dd8525fc00b3f73c30ab4d7
Closes-Bug:#1264245
Merge "Remove return stmt of add,save and remove method"