expose the vRouter port

Change-Id: I23756e9bb854dc79ea38c475f7eb9d70fcd19168
diff --git a/roles/onos-fabric-install/files/onos-fabric-docker-compose.yml b/roles/onos-fabric-install/files/onos-fabric-docker-compose.yml
index b9bc37d..76d64cd 100644
--- a/roles/onos-fabric-install/files/onos-fabric-docker-compose.yml
+++ b/roles/onos-fabric-install/files/onos-fabric-docker-compose.yml
@@ -6,8 +6,9 @@
    xos-onos:
       image: docker-registry:5000/onosproject/onos:candidate
       ports:
-       - "6653:6653"
-       - "8101:8101"
-       - "8181:8181"
-       - "9876:9876"
+       - "6653:6653" # OpenFlow
+       - "8101:8101" # ONOS SSH
+       - "8181:8181" # ONOS UI/API
+       - "9876:9876" # ONOS Clustering
+       - "2620:2620" # vRouter