Windows: Cleanup HCS on restore

Signed-off-by: John Howard <jhoward@microsoft.com>

This ensures that any compute processes in HCS are cleanedup
during daemon restore. Note Windows cannot (currently) reconnect
to containers on restore.

libcontainerd/client_windows.go

@@ -557,8 +557,22 @@ func (clnt *client) Stats(containerID string) (*Stats, error) {
 
 // Restore is the handler for restoring a container
 func (clnt *client) Restore(containerID string, _ StdioCallback, unusedOnWindows ...CreateOption) error {
-	// TODO Windows: Implement this. For now, just tell the backend the container exited.
 	logrus.Debugf("libcontainerd: Restore(%s)", containerID)
+
+	// TODO Windows: On RS1, a re-attach isn't possible.
+	// However, there is a scenario in which there is an issue.
+	// Consider a background container. The daemon dies unexpectedly.
+	// HCS will still have the compute service alive and running.
+	// For consistence, we call in to shoot it regardless if HCS knows about it
+	// We explicitly just log a warning if the terminate fails.
+	// Then we tell the backend the container exited.
+	if hc, err := hcsshim.OpenContainer(containerID); err == nil {
+		if err := hc.Terminate(); err != nil {
+			if !hcsshim.IsPending(err) {
+				logrus.Warnf("libcontainerd: failed to terminate %s on restore - %q", containerID, err)
+			}
+		}
+	}
 	return clnt.backend.StateChanged(containerID, StateInfo{
 		CommonStateInfo: CommonStateInfo{
 			State:    StateExit,