Using openonu-go 1.2.8 in openonu chart 2.7.15

Change-Id: Iba86babbc7394eb1abca98b32c31ac1f7d050f86
diff --git a/voltha-adapter-openonu/Chart.yaml b/voltha-adapter-openonu/Chart.yaml
index f1ef6a3..5fb6bfb 100644
--- a/voltha-adapter-openonu/Chart.yaml
+++ b/voltha-adapter-openonu/Chart.yaml
@@ -14,7 +14,7 @@
 ---
 apiVersion: "v1"
 name: "voltha-adapter-openonu"
-version: "2.7.14"
+version: "2.7.15"
 description: "A Helm chart for Voltha OpenONU Adapter"
 keywords:
   - "onf"
@@ -33,4 +33,4 @@
 
 # appVersion refers to multiple components with potentially different
 # container image versions.
-appVersion: "1.2.7"
+appVersion: "1.2.8"