Update create delete update image tests

* Updated create_image tests
- Updated tests due to behavior, fixture and config changes
- Updated variables for better clarity
- Updated import order
* Updated create_image_negative tests
- Updated tests due to behavior, fixture and config changes
- Updated method call reference
- Split public validation test into two tests
- Updated image_names to a list comprehension
- Updated import order
- Updated test name
- Added skipif tags for certain tests
- Updated create_public_image test to account for different env
* Updated delete_image tests
- Updated tests due to behavior, fixture and config changes
- Updated import order
* Updated delete_image_negative tests
- Updated tests due to behavior, fixture and config changes
- Updated import order
- Updated test step wording
* Updated delete_image_positive tests
- Updated tests due to behavior, fixture and config changes
- Updated method call reference
- Updated skipped test to account for superuser config
- Updated to check for False instead of None for superuser config
- Updated import order
* Updated update_image tests
- Updated tests due to behavior, fixture and config changes
- Updated import order
* Updated update_image_negative tests
- Updated tests due to behavior, fixture and config changes
- Updated method call reference
- Moved the second test for public validation here
- Updated image creations
- Update image_names to a list comprehension
- Updated imported order
- Updated test name
- Updated _validate_update_image_fails name
* Updated update_image_positive tests
- Updated tests due to behavior, fixture and config changes
- Updated import order

Change-Id: I1590dbf244c433a68d8a9f4eb75f34a2a5c6f0c0
Merge "Update create delete update image tests"