nsinit.DefaultCreateCommand sets Pdeathsig to SIGKILL

Docker-DCO-1.1-Signed-off-by: Bernerd Schaefer <bj.schaefer@gmail.com> (github: bernerdschaefer)

pkg/libcontainer/nsinit/exec.go

@@ -123,6 +123,7 @@ func DefaultCreateCommand(container *libcontainer.Container, console, rootfs, da
 	command.Env = append(os.Environ(), env...)
 
 	system.SetCloneFlags(command, uintptr(GetNamespaceFlags(container.Namespaces)))
+	command.SysProcAttr.Pdeathsig = syscall.SIGKILL
 	command.ExtraFiles = []*os.File{pipe}
 
 	return command