Refactor Images API v2.0 Tenant Permissions Test

Test and fixtures refactoring:
 - refactored the test to account for changes made on the fixtures, behaviors, config and image model
 - used non admin users for the implementation of the tests
 - added new test steps to improve implementation
 - added admin user access data, behavior and images client in the fixtures,
   to distinguish between privileges of a normal user, an alternate user (both non admin) and the admin user.
 - reverted changes on the image fixtures and made it a separate PR.

Refactors the test:
 - added type and regression tags.
 - removed any reference to admin user or tenant
 - added new test steps
 - made changes to get the test run against preprod
 - reordered the imports

Change-Id: Ie0bbffebd655a5be3093d447633b7e3886c0904d
Merge "Refactor Images API v2.0 Tenant Permissions Test"