Add ceph-mgr to Ubuntu Xenial jobs
Add ceph-mgr to Ubuntu Xenial jobs

The Pike release of OpenStack now comes bundled with Ceph 12.x
which requires ceph-mgr in order to run properly.  This patch
installs it.

The ceph-mgr service is not available in 10.x which is what
CentOS ships, we can drop the conditional once CentOS ships
the latest stable Ceph release.

Change-Id: I9b9c63c835770f7632051ac114f8bf6b19e8e210

openstack/puppet-openstack-integration,openstack/puppet-openstack-integration,openstack/puppet-openstack-integration