Remove sigchld reaper from containerd process

Because we are launching alot of different runc commands to do
operations there is a race between doing a `cmd.Wait()` and getting the
sigchld and reaping it.  We can remove the sigchild reaper from
containerd as long as we make sure we reap the shim process if we are
the parent, i.e. not restored.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

containerd/main.go

@@ -134,10 +134,7 @@ func daemon(context *cli.Context) error {
 	// setup a standard reaper so that we don't leave any zombies if we are still alive
 	// this is just good practice because we are spawning new processes
 	s := make(chan os.Signal, 2048)
-	signal.Notify(s, syscall.SIGCHLD, syscall.SIGTERM, syscall.SIGINT)
-	if err := osutils.SetSubreaper(1); err != nil {
-		logrus.WithField("error", err).Error("containerd: set subpreaper")
-	}
+	signal.Notify(s, syscall.SIGTERM, syscall.SIGINT)
 	sv, err := supervisor.New(
 		context.String("state-dir"),
 		context.String("runtime"),
@@ -169,10 +166,6 @@ func daemon(context *cli.Context) error {
 	}
 	for ss := range s {
 		switch ss {
-		case syscall.SIGCHLD:
-			if _, err := osutils.Reap(); err != nil {
-				logrus.WithField("error", err).Warn("containerd: reap child processes")
-			}
 		default:
 			logrus.Infof("stopping containerd after receiving %s", ss)
 			server.Stop()