[WIP] improve ipv6-only cluster function

[uablrek]

This PR is a partial fix for #284 .

This PR adds the ipv6 localhost address [::1]:6445 to be used on an ipv6-only cluster instead of the ipv4 127.0.0.1.

It also adds the ipv6 localhost [::1] to the certificates, both in genTLS and genTokenTLS. This is done always, even in an ipv4-only cluster. Since it is localhost I did not think there will be any security issues(?).

Remaining problem

Access to the k8s api does not work from within a pod. The service endpoint for the kubernetes service is;

# kubectl get service kubernetes
NAME         TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   fd00:4000::1   <none>        443/TCP   2m16s
# kubectl get endpoints kubernetes
NAME         ENDPOINTS    AGE
kubernetes   [::1]:6445   49s

which I think is correct but from within a pod it is not possible to connect to the kubernetes service ip (connection hangs). From main netns it works fine.

I am a bit stuck so I publish this PR with hope of aid from others.

[uablrek]

Obsolete due to dual-stack support in k8s