Update vendor

vendor/github.com/docker/containerd/supervisor/signal.go

@@ -0,0 +1,27 @@
+package supervisor
+
+import "os"
+
+type SignalTask struct {
+	baseTask
+	ID     string
+	PID    string
+	Signal os.Signal
+}
+
+func (s *Supervisor) signal(t *SignalTask) error {
+	i, ok := s.containers[t.ID]
+	if !ok {
+		return ErrContainerNotFound
+	}
+	processes, err := i.container.Processes()
+	if err != nil {
+		return err
+	}
+	for _, p := range processes {
+		if p.ID() == t.PID {
+			return p.Signal(t.Signal)
+		}
+	}
+	return ErrProcessNotFound
+}