tests: update libvirt fake object

commit eb2ef555345a32a4f0153ac0341b4c422cdacf8c
requires the 'close' method to be present.

This patch updates the tests to let 'make check' run cleanly again.

Change-Id: I1bb271d90ca8d20f83ab0af38e96598991115ad2
Signed-off-by: Francesco Romani <fromani@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/27323
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>