[VOL-5064] Release patch repo:voltha-system-tests (branch=voltha-2.12)

VERSION
.gitreview
----------
 o Post release tag & branch patch for branch=voltha-2.12.
 o Bump version string to avoid conflicts:
   - branch=master  (X.{1+Y}.0)
   - branch=release (X.Y.{1+Z})
 o Update .gitreview (defaultpath=voltha-2.12), specify rebase/merge target.

Change-Id: I09390218a26036d1f413bd4b95fa9ec09c7b442c
diff --git a/.gitreview b/.gitreview
index a95e0fb..be9ffe2 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,4 +3,4 @@
 port=29418
 project=voltha-system-tests.git
 defaultremote=origin
-defaultbranch=master
+defaultbranch=voltha-2.12
diff --git a/VERSION b/VERSION
index d94526e..9634e38 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.12.11
+2.12.12