k8s-ndots-search-domain-nxdomain-flood

Fix for massive NxDomain query floods to external DNS servers caused by Kubernetes ndots:5 search domain expansion. Use when: (1) DNS server shows low cache hit rate with 60%+ NxDomain responses, (2) DNS logs show queries like "service.namespace.svc.cluster.local.yourdomain.lan", (3) external DNS receives thousands of junk queries per hour for non-existent names ending in your search domain, (4) DNS cache hit ratio is unexpectedly low despite stable workloads. Applies to any Kubernetes cluster using CoreDNS with a custom DNS search domain.