fix(dns): Fix DNSSEC validation

After some investigation it seems that prefetch causes some issues with
DNSSEC it seems to drop the ad flag on a refresh. Therefore it's
disabled for now.

apps/k8s01/dns/dns.yaml

@@ -24,7 +24,7 @@ data:
     caching:
       minTime: 5m
       maxItemsCount: 262144
-      prefetching: true
+      prefetching: false
       prefetchMaxItemsCount: 131072
     prometheus:
       enable: true