Require libvirt that allows vmUpdateDevice

Change-Id: I50b9af97887c2e00e87d34620153a82e28c2a310
Bug-Url: https://bugzilla.redhat.com/1001001
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/18937
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>