* Always Close() the Worker instance
* orchard list vms: show assigned worker for each of the VMs
* Stop the failed VMs before we schedule new VMs
To avoid violating resource constraints.
* syncOnDiskVMs: don't ignore running VMs
* Worker: show correct remote and local VM counts
* Implement restart policy for VMs
* Do not update VM.Resource, we only use it as a read-only specification
* Err()/setErr(): use atomic.Pointer instead of sync.Mutex
Nikolay Edigaryev