Medium: VirtualDomain: destroy domain shortly before timeout expiry

As lmb pointed out in private email, the VirtualDomain RA is not
as persistent on stop as it should be. This patch employs the
following logic:

• If force_stop is unset and a stop operation is issued, invoke "virsh shutdown" and loop on monitor for (x-5) seconds, where x is the operation timeout passed received from the CRM. If the domain is still alive by then, kill it with "virsh destroy".

• If force_stop is set and a stop operation is issued, invoke "virsh destroy" outright.