Move few docker_images* under 'defaults' logic

   * Move all docker-images-artifacts under one class
   * This patch affect only:
     - docker-images CI\CD

Change-Id: I534c3a1d642bfb522e4ae8f195906de8f9ee718e
diff --git a/docker/swarm/stack/postgresql.yml b/docker/swarm/stack/postgresql.yml
index 42ebf8f..192b82c 100644
--- a/docker/swarm/stack/postgresql.yml
+++ b/docker/swarm/stack/postgresql.yml
@@ -1,7 +1,6 @@
 parameters:
   _param:
     docker_postgresql_replicas: 1
-    docker_image_postgresql: library/postgres:9.6
     postgresql_bind_host: postgresql-db
     postgresql_bind_port: ${_param:haproxy_postgresql_bind_port}
     postgresql_ssl:
@@ -29,4 +28,4 @@
           network:
             default:
               external:
-                name: oss_backend
\ No newline at end of file
+                name: oss_backend