[Aether-1761] - Refactor the imagePullSecret for migrating to Fleet

- Avoid to input the credential in helm values.
- Use the sealsecret object in Fleet deployment.

Change-Id: I8036b48caeb23df18622b144cc540386de452705
diff --git a/apps/dbuf/templates/deployment.yaml b/apps/dbuf/templates/deployment.yaml
index 9eb0822..41c0357 100644
--- a/apps/dbuf/templates/deployment.yaml
+++ b/apps/dbuf/templates/deployment.yaml
@@ -22,10 +22,10 @@
       labels:
         {{- include "dbuf.selectorLabels" . | nindent 8 }}
     spec:
-      {{- if .Values.image.credentials }}
+    {{- if hasKey .Values.image "pullSecrets" }}
       imagePullSecrets:
-        - name: {{ .Release.Name }}.registry
-      {{- end }}
+{{ toYaml .Values.image.pullSecrets | indent 8 }}
+    {{- end }}
       securityContext:
         {{- toYaml .Values.podSecurityContext | nindent 8 }}
       containers: