IP_FAMILY selects ipv4, ipv6 or dual and becomes networking.ipFamily, leaving
kind's per-family subnet defaults alone. The script also recreates a pre-IPv6
"kind" Docker network, fails fast if the daemon has IPv6 off, sets proxy_ndp
alongside proxy_arp for gVisor pod-to-pod traffic, and repoints an ipv6
kubeconfig from [::1] at localhost so a client outside the Docker host can
still reach the apiserver.
Tested on kind with all three families: node InternalIPs, Service ClusterIPs
and pod IPs land in the requested families, pod-to-pod and CoreDNS work on
them, and pods still pull through the local registry.
Yuan Gao
1377f858ec