This changes clientcmd to skip the default cluster, but preserves the
behavior in kubectl. This prevents the possibility of an administrator
misconfiguration in kubelet or other server component from allowing a
third party who can bind to 8080 on that host from potentially
impersonating an API server and gaining root access.
In the getting started example of AWS, the master uses an IP that is changed on
stop/start. If you are playing with a cluster and stop and start the master,
the IP is changed and you can't connect again, even using the
"--insecure-skip-tls-verify" option.
This patch fixes it and makes the option work on those cases too by making
sure no CA/CAData is added when it shouldn't.
