Post release increment to version 2.2.0-dev

Change-Id: I4ff2401366012b31ea14bd50c7a99cdd236746e5
diff --git a/VERSION b/VERSION
index 7ec1d6d..97ade15 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.1.0
+2.2.0-dev