Automatic merge from submit-queue
Update port forward e2e for go 1.6
Only close the stdout/stderr pipes from kubectl port-forward when we're truly done with the command,
instead of as soon as runPortForward exits.
Also try to gracefully stop kubectl port-forward via SIGINT, instead of always sending SIGKILL, as
this will help avoid spdy goroutine leaks in the Kubelet.
Ref #22149
cc @smarterclayton @kubernetes/rh-cluster-infra