Switch to common oss overlay network

Change-Id: I60dde93b161d2be6ef0523c41254f0a761261b4c
diff --git a/docker/swarm/stack/devops_portal.yml b/docker/swarm/stack/devops_portal.yml
index f553114..f8f89f9 100644
--- a/docker/swarm/stack/devops_portal.yml
+++ b/docker/swarm/stack/devops_portal.yml
@@ -18,3 +18,9 @@
               volumes:
                 - /srv/volumes/devops_portal/nginx:/etc/nginx/config
                 - /srv/volumes/devops_portal/config:/opt/devops-portal/config
+          network:
+            default:
+              external:
+                name: oss_backend
+            frontend:
+              driver: overlay
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