fix tests (#588)

fix proxy_three_node_disconnect_test and hole_punching_symmetric_only_random

easytier/src/connector/udp_hole_punch/sym_to_cone.rs

@@ -529,6 +529,7 @@ pub mod tests {
     };
 
     #[tokio::test]
+    #[serial_test::serial]
     #[serial_test::serial(hole_punch)]
     async fn hole_punching_symmetric_only_random() {
         RUN_TESTING.store(true, std::sync::atomic::Ordering::Relaxed);