Remove unused driver attr in cinder_backends map
Remove unused driver attr in cinder_backends map

Change-Id: Ib684e3f4bcd26e40c5bfde9bec8a1d83563d5460
Signed-off-by: Pavel Glushchak <a01950bf8d7d49f8f7ea5c1c62fa9db3304a0d63@virtuozzo.com>

dardelean/kolla-ansible,dardelean/kolla-ansible,dardelean/kolla-ansible