Mount bind cache as empty dir

deployments/dns/bind.yaml

@@ -118,6 +118,8 @@ spec:
         - name: dns-secrets
           mountPath: /etc/bind/externaldns-key.conf
           subPath: externaldns-key.conf
+        - name: bind-cache
+          mountPath: /var/cache/bind
       volumes:
       - name: dns-secrets
         secret:
@@ -125,6 +127,8 @@ spec:
       - name: config
         configMap:
           name: bind-master-config
+      - name: bind-cache
+        emptyDir: {}
 ---
 apiVersion: apps/v1
 kind: DaemonSet