[CORD-3026] Unify the usage of imagePullPolicy in helm-charts

Change-Id: I6135a81060eeb7f2831ce9c7207339f92017c10e
diff --git a/voltha/templates/grafana.yaml b/voltha/templates/grafana.yaml
index 4fa7566..f4716bb 100644
--- a/voltha/templates/grafana.yaml
+++ b/voltha/templates/grafana.yaml
@@ -63,7 +63,8 @@
       serviceAccountName: {{ .Values.global.namespace }}-serviceaccount
       containers:
       - name: grafana
-        image: {{ .Values.pull_docker_registry }}{{ .Values.images.grafana.repository }}:{{ .Values.images.grafana.tag }}
+        image: {{ .Values.grafanaImage }}
+        imagePullPolicy: {{ .Values.imagePullPolicy }}
         ports:
         - containerPort: 80
         - containerPort: 2003