Parametrize mcp_docker_registry host

Related-Bug: PROD-22480 (PROD:22480)

Change-Id: I36ad55a1960f6c8e025d9c967bbc7658927fc872
diff --git a/docker/swarm/stack/pushkin.yml b/docker/swarm/stack/pushkin.yml
index 55f1fd6..65d400e 100644
--- a/docker/swarm/stack/pushkin.yml
+++ b/docker/swarm/stack/pushkin.yml
@@ -1,7 +1,8 @@
 parameters:
   _param:
+    mcp_docker_registry: 'docker-prod-local.artifactory.mirantis.com'
     docker_pushkin_replicas: 1
-    docker_image_pushkin: docker-prod-local.artifactory.mirantis.com/mirantis/oss/pushkin
+    docker_image_pushkin: ${_param:mcp_docker_registry}/mirantis/oss/pushkin
     pushkin_bind_host: pushkin-api
     pushkin_bind_port: ${_param:haproxy_pushkin_bind_port}
     pushkin_elasticsearch: ${_param:elasticsearch_bind_host}