GET v2.0/image/{image_id}/members

- remove custom MSG import
- put ImagesConfig and AdminUserConfig imports on same line
- implement image sharing tests
- solve pep8 formatting errors for comments
- remove a file that was not part of the PR.
- address reviewer comments.

Change-Id: Ied69741aa8a664cf57a2de11f0475378ea26ee55
Merge "GET v2.0/image/{image_id}/members"