[k8s] Fail to ssh into the head node on k8s

[alex000kim]

The cluster launches and executes the task sucessfully:

sky launch -c test --cloud kubernetes -- echo hi

I fail to ssh into it:

$ ssh test
Bad stdio forwarding specification '2600:1f16:cf3:2521:cf7c::8:22'
Connection closed by UNKNOWN port 65535

[romilbhardwaj]

Thanks for the report @alex000kim! Looks like this is related to running on a k8s cluster with ipv6. Two steps for us:

1. Replicate on our end.
2. Fix our proxycommand script to have socat/kubectl port-forward work with ipv6.

[romilbhardwaj]

Closed with #4497.