After introducing the change Iead5167210c4132badb866afc25d4ef14e27f6b2
swift isn't installed if ceph used as a backend for images
and not for object-storage service. In this sutiation we end up
with absence of object-storage at all which is wrong.
The commit introduces changes which makes possible
to swift been installed if ceph used only for image service.
Change-Id: If319845aa9f2d9b3ca07936350ef374f504679cb
Closes-Bug: #1604879