VOL-2894 - reference the voltha GRPC end point via a holder

Change-Id: If24299556ad6cacf9cd0f793167a2c908534729c
(cherry picked from commit f8ce7d2ceaf5c37cc992448e7c6b6331a234168b)
diff --git a/.gitreview b/.gitreview
index c04b89f..0d921fa 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,3 +3,4 @@
 port=29418
 project=ofagent-go.git
 defaultremote=origin
+defaultbranch=voltha-2.3