app-emulation/libvirt: update libvirt-guests.init openrc script

app-emulation/libvirt: update libvirt-guests.init openrc script

From the bug report:

  """
  When libvirt-guests tries to shutdown or suspend xen guests, it is
  unable to tell when all of the guests have terminated and ends up
  waiting the entire timeout before going on. This is because in xen,
  dom0 is always running. Simply grepping out the dom0 uuid (all 0s)
  should take care of this issue.
  """

Thanks to Karl Hakimian for bug report and patch.

This is fixed in versions 4.6.0-r1 and 9999.

Closes: https://bugs.gentoo.org/651598
Package-Manager: Portage-2.3.47, Repoman-2.3.10