Method get_server_vc

include/proxy/http/HttpSM.h:311–319

  History<HISTORY_DEFAULT_SIZE> history;
  NetVConnection *
  get_server_vc()
  {
    if (server_entry != nullptr) {
      return dynamic_cast<NetVConnection *>(server_entry->vc);
    } else {
      return nullptr;
    }
  }

  // _postbuf api
  int64_t         postbuf_reader_avail();