Bumping minor versions after VOLTHA-2.7 release

Change-Id: I9acfc611280826f13ec4845f3f2932e1d42571f4
diff --git a/voltha-adapter-openonu/Chart.yaml b/voltha-adapter-openonu/Chart.yaml
index 5fb6bfb..f18efec 100644
--- a/voltha-adapter-openonu/Chart.yaml
+++ b/voltha-adapter-openonu/Chart.yaml
@@ -14,7 +14,7 @@
 ---
 apiVersion: "v1"
 name: "voltha-adapter-openonu"
-version: "2.7.15"
+version: "2.8.0-dev"
 description: "A Helm chart for Voltha OpenONU Adapter"
 keywords:
   - "onf"