Update the kubelet with the ability to register itself with the master.

See #2303
You said that you wanted to tackle registration in this PR, and authentication in another one.  That's fine by me.  In that case, how about deleting line 80 above, and line 89.  You can still test out this code `--auth_path` flag and the `--api_servers` flag.  And then we can revisit those lines in a later PR.