Improve test/utils.py

Introduce new class into utils.py to keep glance api tests DRYer

Partially implements blueprint glance-tests-code-duplication

Change-Id: Ic77961fcc83806fd451afa1a0d230f09926ebfd9
Refactor glance/tests/unit/v2/test_registry_client.py

Remove code duplication from module

Partially implements blueprint glance-tests-code-duplication

Change-Id: Idf54d98d0982b7c64696056c87283eb92f1164b5
The V2 Api should delete a non existent image

Glance V2 api initiates the deletion of an image that
got deleted during upload. This ensures that there
are no orphaned chunks of the image left behind

Fixes bug #1226013

Change-Id: I4cf5c49d2a6d2157a38467d9f7bcb20c4562b642
Merge "The V2 Api should delete a non existent image"
Merge "Improve test/utils.py"
Merge "Refactor glance/tests/unit/v2/test_registry_client.py"