VOL-5115 - Create release branch voltha-2.12-beta

VERSION
-------
  o Increment version string to avoid future conflicts with beta branch.
  o Suffix *-dev on version string for post-release checkins.

Change-Id: I3bff407cb84f74720e24d98a7a98d21b11baade7
diff --git a/VERSION b/VERSION
index cd57a8b..08ec77d 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.1.5
+2.1.6-dev