kubernetes: `port-forward` API call does not support websockets, SPDY is still default.

While the exec and logs calls have been updated to be able to use websockets, the port-forward call is still stuck on SPDY.

We should enable port-forward over websockets.

PR that made the original switch for exec and logs I believe is: https://github.com/kubernetes/kubernetes/pull/13885

and the work to be done should be in pkg/kubelet/server/remotecommand

probably using pk/util/wsstream