message: Fix handshake in incoming_stream_multiplexer
diff: @@ -67,7 +67,7 @@ void incoming_stream_multiplexer::operator()(stream_msg::open& x) {
  auto ptr = make_mailbox_element(
  cme->sender, cme->mid, std::move(cme->stages),
  make<stream_msg::open>(current_stream_msg_->sid, std::move(x.msg),
  - self_->ctrl(), successor, x.priority,
  + self_->ctrl(), x.original_stage, x.priority,
  x.redeployable));
  successor->enqueue(std::move(ptr), self_->context());
  // Send out demand upstream.
  