[VOL-2372]v2 ofagent-go version bumps for 2.3 release

Cherry pick of: https://gerrit.opencord.org/c/18549/

Change-Id: I913e7dd9e4e629e3ae614c488d9058885d2b6bcd
diff --git a/VERSION b/VERSION
index 276cbf9..32d1656 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.3.0
+2.3.1-dev