Starting onos-1.6 support branch

Change-Id: I4d9d7052661480f6c1f607ada1c03534f0ec5156
diff --git a/.gitreview b/.gitreview
index 328aec6..83e0bbd 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,4 +3,4 @@
 port=29418
 project=onos.git
 defaultremote=origin
-defaultbranch=master
+defaultbranch=onos-1.6