VOL-4229: Bump minor version post voltha-2.8 release tagging

Change-Id: I81e692686d0b9ce6e290ef5824e96aa890d53c2f
diff --git a/VERSION b/VERSION
index 1df3b82..de023c9 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.6.10
+1.7.0-dev