Images API v2.0 Remove All Shared Images From User List

Implements remove all shared images from user list test:
 - added a test scenario 'remove all shared images from user list'.
 - refactored image fixtures.
 - reverted changes on image fixtures and made it a separate PR.
 - improved naming of variables.

Refactors test to add tags.

Change-Id: Ia8d48102758e0d0799590c5ab0ec5411a6457228
Merge "Images API v2.0 Remove All Shared Images From User List"