This reverts commit
The _is_storage_shared_with method is specifically checking if the
instance directory is shared. It is not checking if the actual instance
disks are shared and as a result assumptions cannot be made based on the
value of images_type.
(cherry picked from commit 404932f82130445472837095b3ad9089c75e2660)
(cherry picked from commit 890882ebbf74db14a7c1904cca96cd7f5907493b)