test: add test for restart on new container image

Since we have a task to test the handlers we can test a new container to
validate the service restart on a new container image.

Signed-off-by: Sébastien Han <seb@redhat.com>

tests/functional/centos/7/cluster/ceph-override.json

@@ -5,4 +5,5 @@
 			"osd_pool_default_size": 1
 		}
 	}
+  "ceph_docker_image_tag": "tag-stable-3.0-luminous-ubuntu-16.04"
 }