message: Fix endless error loop between two stream servers
diff: @@ -103,6 +103,7 @@ void stream_multiplexer::fail(error reason, strong_actor_ptr predecessor,
  unsafe_send_as(self_, successor,
  make<stream_msg::abort>(current_stream_msg_->sid, reason));
  auto rp = self_->make_response_promise();
  + if (!rp.async())
  rp.deliver(std::move(reason));
  }
  