Remove auto network thread thing

src/config.hpp

@@ -19,7 +19,7 @@ struct ServerConfig {
   /// Number of accept threads for handling incoming connections
   int accept_threads = 1;
   /// Number of network I/O threads for epoll processing
-  int network_threads = 0; // 0 means use hardware_concurrency
+  int network_threads = 1;
   /// Event batch size for epoll processing
   int event_batch_size = 32;
 };