Update images fixture

*Added object storage integration fixture and teardown
*Removed admin user configurations
*Added an updated variables
*Added class cleanup
*Updated compute integration fixture
*Updated fixture to use alt_url where needed
*Removed _upload_file_data method that is no longer needed
*Removed ObjectStorageIntegrationFixture teardown

Change-Id: I20ea5273b6bb9ded2da42575afb50914f9e66c44