livecd-bashrc: Avoid a startx race by restricting to tty1

livecd-bashrc: Avoid a startx race by restricting to tty1

Otherwise several virtual consoles may notice the existence of
/etc/startx, and spawn simultaneous X servers.  This way we only spawn
a single X server, regardless of timing.

A better solution here is probably to add a "start" or "x-server"
service to /etc/init.d/, but that's more work than I'm up to at the
moment.