Fix iscsi and tgt containers deployment case
Fix iscsi and tgt containers deployment case

In the following config:
enable_cinder=False
enable_cinder_backend_iscsi=True

Iscsi and tgt containers are deployed but should not.
This patch fix it.

Change-Id: I1d66627b9979b5dc570bbc3e1e865311dd7e7bb0
Closes-Bug: #1715618

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