Use cluster_name variable instead of hardcoded value in cinder-csi controller plugin (kubernetes-sigs#10422)

Author: floryut

roles/kubernetes-apps/csi_driver/cinder/templates/cinder-csi-controllerplugin.yml.j2

@@ -111,7 +111,7 @@ spec:
             - name: CLOUD_CONFIG
               value: /etc/config/cloud.conf
             - name: CLUSTER_NAME
-              value: kubernetes
+              value: {{ cluster_name }}
           ports:
             - containerPort: 9808
               name: healthz