Move the DockerConn flush to its own function

Upstream-commit: c83393a541353ab34612d80cc6b9bb4e92c59597
Component: engine

components/engine/commands.go

@@ -894,7 +894,7 @@ func (srv *Server) CmdRun(stdin io.ReadCloser, stdout rcli.DockerConn, args ...s
 	if config.Tty {
 		stdout.SetOptionRawTerminal()
 		// Flush the options to make sure the client sets the raw mode
-		stdout.Write([]byte{})
+		stdout.Flush()
 	}
 
 	// Create new container

components/engine/rcli/tcp.go

@@ -92,6 +92,11 @@ func (c *DockerTCPConn) Write(b []byte) (int, error) {
 	return n + optionsLen, err
 }
 
+func (c *DockerTCPConn) Flush() error {
+	_, err := c.conn.Write([]byte{})
+	return err
+}
+
 func (c *DockerTCPConn) Close() error { return c.conn.Close() }
 
 func (c *DockerTCPConn) CloseWrite() error { return c.conn.CloseWrite() }

components/engine/rcli/types.go

@@ -29,6 +29,7 @@ type DockerConn interface {
 	CloseRead() error
 	GetOptions() *DockerConnOptions
 	SetOptionRawTerminal()
+	Flush() error
 }
 
 type DockerLocalConn struct {
@@ -56,6 +57,8 @@ func (c *DockerLocalConn) Close() error {
 	return c.writer.Close()
 }
 
+func (c *DockerLocalConn) Flush() error { return nil }
+
 func (c *DockerLocalConn) CloseWrite() error { return nil }
 
 func (c *DockerLocalConn) CloseRead() error { return nil }