VOL-2630 return to -dev version

Change-Id: I4b60bf4cdd45fc0d78dbccce8f78b10e36308e96
diff --git a/VERSION b/VERSION
index 276cbf9..32d1656 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.3.0
+2.3.1-dev