Images API v2.0 Image Visibility Of Images Owned by User

Implements image visibility of images owned by a particular user test:
 - added a test scenario for image visibility of images owned by a particular user.
 - refactored image fixtures.
 - reverted changes on the image fixtures and made it a separate PR.
 - improved naming of variables.

Refactors the test:
 - added the tags
 - added a new line.
 - improved naming of tests
 - inlined a test step.

Change-Id: Iff00050ce502ceea3f4a4675630169a7ec67cce1
Merge "Images API v2.0 Image Visibility Of Images Owned by User"