Use the staging release image as default

Also, use the existing image pull secret

Change-Id: Ia92b116c7127a8e6d619cff2418d827d47779521
diff --git a/omec/omec-upf-pfcp-agent/templates/statefulset-pfcp-agent.yaml b/omec/omec-upf-pfcp-agent/templates/statefulset-pfcp-agent.yaml
index 002a6ac..5ee03b0 100644
--- a/omec/omec-upf-pfcp-agent/templates/statefulset-pfcp-agent.yaml
+++ b/omec/omec-upf-pfcp-agent/templates/statefulset-pfcp-agent.yaml
@@ -28,9 +28,9 @@
       nodeSelector:
         {{ .Values.nodeSelectors.pfcp.label }}: {{ .Values.nodeSelectors.pfcp.value }}
     {{- end }}
-    {{- if .Values.images.credentials }}
+    {{- if hasKey .Values.images "pullSecrets" }}
       imagePullSecrets:
-        - name: {{ .Release.Name }}.registry
+{{ toYaml .Values.images.pullSecrets | indent 8 }}
     {{- end }}
     {{- if .Values.config.coreDump.enabled }}
       initContainers: