Low: VirtualDomain: Avoid potentially blocking 'virsh' execution during meta-data action

We need meta-data actions to be fast.  Forking the call to 'virsh' to determine the default uri is causing some problems with pacemaker.  Pacemaker has to retrieve agent's meta-data to determine if things like reloads are possible.  To avoid blocking the crmd, pacemaker places a very short timeout period on these operations.  VirtualDomain actually hits time timeout period because the 'virsh' fork sometimes blocks for a short period of time.