Update containerd and leverage plugin graceful stop.

Signed-off-by: Lantao Liu <lantaol@google.com>

vendor/github.com/opencontainers/runc/libcontainer/system/linux.go

@@ -134,3 +134,14 @@ func RunningInUserNS() bool {
 func SetSubreaper(i int) error {
 	return unix.Prctl(PR_SET_CHILD_SUBREAPER, uintptr(i), 0, 0, 0)
 }
+
+// GetSubreaper returns the subreaper setting for the calling process
+func GetSubreaper() (int, error) {
+	var i uintptr
+
+	if err := unix.Prctl(unix.PR_GET_CHILD_SUBREAPER, uintptr(unsafe.Pointer(&i)), 0, 0, 0); err != nil {
+		return -1, err
+	}
+
+	return int(i), nil
+}