[libvirt] suspend/hibernate guests on host shutdown

[Gerry Reno]

There are times when you just have to reboot the host machine to clear a 
problem or after some maintenance.  The problem right now is that this 
forces all the guests to go through an entire reboot as well.  What 
would be good is if the host shutdown would invoke a suspend/hibernate 
of the guests and then restore the guests to their same condition on the 
reboot.  The guests should notice nothing other that a small loss of 
wallclock time.

Regards,
Gerry