Create 2.6 support branch

Change-Id: I2c80fe9baddf2030ad404a0a753aac502e4c3d1e
diff --git a/.gitreview b/.gitreview
index 328aec6..9ef2cc2 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,4 +3,4 @@
 port=29418
 project=onos.git
 defaultremote=origin
-defaultbranch=master
+defaultbranch=onos-2.6