Signed-off-by: Valerio Pachera <sirio81@gmail.com>
Signed-off-by: Valerio Pachera <sirio81@gmail.com>

Use miltithread for 'cluster shutdown_guest'.

When invoked, 'cluster shutdown_guest' run 'host shutdown_guests'
on alle nodes but one after the otehr.
Using miltithread is possible to run 'host shutdown_guest' on all
nodes at the same time.

sirio81/vmcli,sirio81/vmcli