[libvirt] autostart with xend

[John Levon <levon movementarian org>]

It doesn't work quite right with a running domain. The 'new' will
correctly set the config, but the temporary config doesn't include the
new setting. So tests of the form "set autostart; is it set?" will fail.

Suggestions?

Also, why isn't this represented in the XML?

thanks,
john