message: Close slots individually in close()
diff: @@ -113,12 +113,9 @@ bool downstream_manager::clean(stream_slot slot) const noexcept {
  void downstream_manager::close() {
  CAF_LOG_TRACE("");
  - if (clean()) {
  - for_each_path([&](outbound_path& x) { about_to_erase(&x, false, nullptr); });
  - clear_paths();
  - } else {
  - for_each_path([&](outbound_path& x) { x.closing = true; });
  - }
  + auto slots = path_slots();
  + for (auto slot : slots)
  + close(slot);
  }
  void downstream_manager::close(stream_slot slot) {
  