VOL-5132 - Create beta-release branch for voltha-lib-go

.gitreview
----------
  o Assign defaultbranch= for merge/rebase into release branch.

VERSION
-------
  o Bump version string to avoid future conflicts with master branch.

Change-Id: I05547704e5049391901b01d77a6c798aa0d85337
diff --git a/.gitreview b/.gitreview
index bf04ac9..8323c7a 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,3 +3,4 @@
 port=29418
 project=voltha-lib-go.git
 defaultremote=origin
+defaultbranch=voltha-2.12
diff --git a/VERSION b/VERSION
index bd8293a..25627bc 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-7.4.6
+7.4.7