message: Send open_stream_msg with proper sender handle
diff: @@ -198,7 +198,8 @@ int32_t stream_manager::acquire_credit(inbound_path*, int32_t desired) {
  return desired;
  }
  -stream_slot stream_manager::add_unchecked_outbound_path_impl(response_promise& rp,
  +stream_slot
  +stream_manager::add_unchecked_outbound_path_impl(response_promise& rp,
  message handshake) {
  CAF_LOG_TRACE(CAF_ARG(rp) << CAF_ARG(handshake));
  CAF_ASSERT(out().terminal() == false);
  @@ -217,14 +218,16 @@ stream_slot stream_manager::add_unchecked_outbound_path_impl(response_promise& r
  return slot;
  }
  -stream_slot stream_manager::add_unchecked_outbound_path_impl(strong_actor_ptr next,
  +stream_slot
  +stream_manager::add_unchecked_outbound_path_impl(strong_actor_ptr next,
  message handshake) {
  CAF_LOG_TRACE(CAF_ARG(next) << CAF_ARG(handshake));
  - response_promise rp{self_->ctrl(), nullptr, {next}, make_message_id()};
  + response_promise rp{self_->ctrl(), self_->ctrl(), {next}, make_message_id()};
  return add_unchecked_outbound_path_impl(rp, std::move(handshake));
  }
  -stream_slot stream_manager::add_unchecked_outbound_path_impl(message handshake) {
  +stream_slot
  +stream_manager::add_unchecked_outbound_path_impl(message handshake) {
  CAF_LOG_TRACE(CAF_ARG(handshake));
  auto rp = self_->make_response_promise();
  return add_unchecked_outbound_path_impl(rp, std::move(handshake));
  