Update ONOS version to 1.6.0-rc4

Also add a .gitreview file

Change-Id: I73f372383ea00ed003dc13c140bc713ea393b4d9
diff --git a/.gitreview b/.gitreview
new file mode 100644
index 0000000..1d85e91
--- /dev/null
+++ b/.gitreview
@@ -0,0 +1,6 @@
+[gerrit]
+host=gerrit.opencord.org
+port=29418
+project=cord-onos-publisher.git
+defaultremote=origin
+defaultbranch=master
diff --git a/apps/vtn b/apps/vtn
index 5dea585..60a1067 160000
--- a/apps/vtn
+++ b/apps/vtn
@@ -1 +1 @@
-Subproject commit 5dea58580ca1d3965b5e575139ada1c50c4e3101
+Subproject commit 60a10679683ccaa29fc85492343a9d5c79905a0f