Releasing version 2.7.0 of the charts

Change-Id: I75d649aa7e0b9f60b8375574fb3cd5d6ec871cd3
diff --git a/.gitreview b/.gitreview
index 2b11b97..fc8c05c 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,3 +3,4 @@
 port=29418
 project=voltha-helm-charts.git
 defaultremote=origin
+defaultbranch=voltha-2.7