VOL-1797 - fix helm lint issues

Change-Id: I74ccff1f7f431e05fc3963d0707382f478a010f0
diff --git a/voltha-adapter-openolt/templates/adapters-openolt.yaml b/voltha-adapter-openolt/templates/adapters-openolt.yaml
index 83a352b..e4b9f1b 100644
--- a/voltha-adapter-openolt/templates/adapters-openolt.yaml
+++ b/voltha-adapter-openolt/templates/adapters-openolt.yaml
@@ -38,9 +38,17 @@
       containers:
         - name: adapter-open-olt
           {{- if .Values.use_go }}
-          image: {{ tpl .Values.images.adapter_open_olt.registry . }}{{ tpl .Values.images.adapter_open_olt.repository . }}:{{ tpl .Values.images.adapter_open_olt.tag_go . }}
+          {{- $image_tag := tpl .Values.images.adapter_open_olt.tag_go . }}
+          {{- if eq "::DEFAULT::" $image_tag }}
+          {{- $image_tag = .Values.defaults.default_go_image_tag }}
+          {{- end }}
+          image: {{ tpl .Values.images.adapter_open_olt.registry . }}{{ tpl .Values.images.adapter_open_olt.repository . }}:{{ $image_tag }}
           {{- else }}
-          image: {{ tpl .Values.images.adapter_open_olt.registry . }}{{ tpl .Values.images.adapter_open_olt.repository . }}:{{ tpl .Values.images.adapter_open_olt.tag . }}
+          {{- $image_tag := tpl .Values.images.adapter_open_olt.tag . }}
+          {{- if eq "::DEFAULT::" $image_tag }}
+          {{- $image_tag = .Values.defaults.default_py_image_tag }}
+          {{- end }}
+          image: {{ tpl .Values.images.adapter_open_olt.registry . }}{{ tpl .Values.images.adapter_open_olt.repository . }}:{{ $image_tag }}
           {{- end }}
           imagePullPolicy: {{ tpl .Values.images.adapter_open_olt.pullPolicy . }}
           args: