fixes for mirror reorganization

Change-Id: Ib43df2ce7f5f15ccb1d42d860ac320b77213fdb5
diff --git a/aptly/server/mirror/ubuntu/xenial/ceph.yml b/aptly/server/mirror/ubuntu/xenial/ceph.yml
index 8972cf2..50afc3e 100644
--- a/aptly/server/mirror/ubuntu/xenial/ceph.yml
+++ b/aptly/server/mirror/ubuntu/xenial/ceph.yml
@@ -1,6 +1,7 @@
 parameters:
   _param:
     ceph_version: luminous
+    apt_mk_version: stable
   aptly:
     server:
       mirror:
@@ -14,4 +15,4 @@
           publisher:
             component: ceph
             distributions:
-              - ubuntu-xenial/nightly
+              - ubuntu-xenial/${_param:apt_mk_version}