Fix V3 image tests according to new image_client

This patch correct the Nova V3 test_image_oneserver
and test_images_negative according to new image_client.
Also remove the create_image config value.

Closes-Bug: #1290221

Change-Id: Iadaf311e37a42b2adaa9d980a10ae251450030d0
Merge "Fix V3 image tests according to new image_client"