qemu: virsh wrapper for qemu events

qemu: virsh wrapper for qemu events

Any new API deserves a good virsh wrapper :)

    qemu-monitor-event [<domain>] [<event>] [--pretty] [--loop] [--timeout <number>]

Very similar to the previous work on 'virsh event'.  For an
example session:

$ virsh -c qemu:///system qemu-monitor-event --event SHUTDOWN&
$ virsh -c qemu:///system start f18-live
Domain f18-live started

$ virsh -c qemu:///system destroy f18-live
Domain f18-live destroyed

event SHUTDOWN at 1391212552.026544 for domain f18-live: (null)
events received: 1

[1]+  Done                    virsh -c qemu:///system qemu-monitor-event --event SHUTDOWN
$

* tools/virsh-domain.c (cmdQemuMonitorEvent): New command.
* tools/virsh.pod (qemu-monitor-event): Document it.

Signed-off-by: Eric Blake <eblake@redhat.com>