Images v2.0 API Ensure Active Image Location Cannot Be Updated

Implements new test scenario:
 - added a new test: ensure that image location for an active
   image cannot be updated
 - removed the teardown class and moved release of resources to the fixtures
 - added release of resources for all user behaviors to the fixtures.

Change-Id: I222519878a66d68a85f8d0c81ee8108be027fa6e