High: VirtualDomain: Attempt to determine vm status even when libvirt is unavailable

When pacemaker does probe operations, VirtualDomain returns
errors when libvirt is not available. It is possible to determine
if a virtual machine is running without libvirt. This patch
introduces this logic for qemu virtual resources. Additional logic
must be used to extend this functionality to things like lxc though.

Resolves: rhbz#1054327