When using a storage backend which depends on the iSCSI protocol, such
as a NetApp or VNX appliance in iSCSI mode, cinder would work only
partially. New volumes could be created, but download to image and
backup routines would not work, and the reason would not be clear from
the logs.
Change-Id: I0bc876fef42b2c2d881c77ea1f65c43b7cc5d798