aptly mirror parametrization

PROD-15379

Change-Id: Icff58138405245e968d63539ec7b0df2a313b6fd
diff --git a/aptly/server/mirror/ubuntu/xenial/grafana.yml b/aptly/server/mirror/ubuntu/xenial/grafana.yml
index 8dbb6ea..4ae2047 100644
--- a/aptly/server/mirror/ubuntu/xenial/grafana.yml
+++ b/aptly/server/mirror/ubuntu/xenial/grafana.yml
@@ -1,16 +1,20 @@
 parameters:
   _param:
     apt_mk_version: stable
+    mirror_grafana-xenial_source: https://packagecloud.io/grafana/stable/debian/
+    mirror_grafana-xenial_distribution: jessie
+    mirror_grafana-xenial_components: main
+    mirror_grafana-xenial_gpgkeys:
+      - D59097AB
   aptly:
     server:
       mirror:
         grafana-xenial:
-          source: https://packagecloud.io/grafana/stable/debian/
-          distribution: jessie
-          components: main
+          source: ${_param:mirror_grafana-xenial_source}
+          distribution: ${_param:mirror_grafana-xenial_distribution}
+          components: ${_param:mirror_grafana-xenial_components}
           architectures: amd64
-          gpgkeys:
-            - D59097AB
+          gpgkeys: ${_param:mirror_grafana-xenial_gpgkeys}
           publisher:
             component: grafana
             distributions: