overcloud: template dir for split ceph deployment (>=17)
overcloud: template dir for split ceph deployment (>=17)

When ceph is deployed separately, the template base directory
should be computed dynamically as it happens a few lines above,
in the "Deploy the nodes" play. Otherwise the deployment fails
on all deployments which don't use the deployment files from 'virt'.

Change-Id: I483919c7c84af19f6de5efa3379b20f2b5d10042

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