Add the ability to activate Nova ceph without Cinder

Prior to this patch, if we wanted to boot a VM in Ceph using
libvirt_image_type we must had Cinder enabled. This patch allows you to
use libvirt_image_type without having Cinder enabled.

Change-Id: Ia61e6effc5a4ccba69f4fa48f6e9984f15bb8979
Signed-off-by: Sébastien Han <sebastien.han@enovance.com>
Merge "Add the ability to activate Nova ceph without Cinder"