virt: typo: unlink is in os not in os.path

When this code path was reached it caused an exception and left the VM
during recovery in 'PAUSED' state and all communication with the guest
was no longer available.

Change-Id: Id588d272e142fc25e6cd0cd2ab5b7385caf45815
Bug-Url: https://bugzilla.redhat.com/1136982
Signed-off-by: Vinzenz Feenstra <vfeenstr@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/33881
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>