Bump minor version post VOLTHA2.4 branch out

Change-Id: I8f94d56f4362d2dead4f4a0339bf8c6218688bde
diff --git a/VERSION b/VERSION
index 18efdb9..0c64b5c 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.1.8
+1.2.0-dev