VOL-4230: Bump minor version post voltha-2.8 release

Change-Id: I65e45a3e506f91b7f7ac02e3588dbe1d0efe6138
diff --git a/VERSION b/VERSION
index 27f9cd3..b57588e 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.8.0
+1.9.0-dev