Add Pty and CloseStdin RPCs

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

linux/shim/init.go

@@ -28,6 +28,7 @@ type initProcess struct {
 	status  int
 	pid     int
 	closers []io.Closer
+	stdin   io.Closer
 }
 
 func newInitProcess(context context.Context, path string, r *shimapi.CreateRequest) (*initProcess, error) {
@@ -83,6 +84,7 @@ func newInitProcess(context context.Context, path string, r *shimapi.CreateReque
 		if err != nil {
 			return nil, err
 		}
+		p.stdin = sc
 		p.closers = append(p.closers, sc)
 	}
 	if socket != nil {
@@ -175,3 +177,7 @@ func (p *initProcess) killAll(context context.Context) error {
 func (p *initProcess) Signal(sig int) error {
 	return syscall.Kill(p.pid, syscall.Signal(sig))
 }
+
+func (p *initProcess) Stdin() io.Closer {
+	return p.stdin
+}