handle_connect(): Don't send anything to non-authorized clients.

handle_connect(): Don't send anything to non-authorized clients.

Currently, if we don't receive a valid authentication request, we send
back an RC4-encrypted error message to the client, which is kind of
pointless since the RC4 keys are not set up at this point.

Of course we could send an unencryted error message in this case,
but in since the peer could be anything, it seems safer to just close
the connection.