Ensure mds key are created before starting ceph-mds

The key is required so that ceph-mds service can pull information from
ceph-mon.

Change-Id: I8e9d53a53eedff0bd8f529ea4bd415331139b862

manifests/profile/mds.pp

@@ -36,6 +36,6 @@ class ceph::profile::mds {
       secret       => $ceph::profile::params::mds_key,
       user         => 'ceph',
       group        => 'ceph'
-    }
+    } -> Service<| tag == 'ceph-mds' |>
   }
 }