Fix reverted patch "Netapp backend job should fail if no netapp backend is available"
Fix reverted patch "Netapp backend job should fail if no netapp backend is available"

RHOSINFRA-1487: Added validation step for external storage backend,
in case if --storage-external is enabled, --storage-config  should be
provided, otherwise 'tripleo-overcloud' ansible playbook will be failed.
Such verification is needed, because if user doesn't provide external
storage config, tripleo will deploy overcloud with a default storage
backend 'lvm' and that's not expected behavior.

Change-Id: Ib1669ccf3e78626586d81b86b5a10138edcc8d99

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared