Add delete image and get image tests

*Updated delete image module to reflect cloud cafe changes
*Updated get image module to reflect cloud cafe changes
*Updated modeules aesthetic consistency
*Removed happy_path from test name
*Updated test steps for delete_image_as_owner_of_shared_image
*Removed test tag for testing purposes
*All delete_image negative tests removed and submitted in this PR:
 https://review.openstack.org/#/c/58040/
*All get_image negative tests removed and submitted in this PR:
 https://review.openstack.org/#/c/58047/
*Moved duplicate validation block into seperate method
*Updated validation to verify every property before an assertion
*Add further verification to delete_image_that_is_public test
*Added validation for the specific image status

Change-Id: I088a85cdffb23a0fb99a1bd3d09996dd074e019c
Merge "Add delete image and get image tests"