完善之前提交

vllm/distributed/kv_transfer/kv_connector/v1/du/du_swift_engine.py

@@ -1014,6 +1014,7 @@ class DuSwiftEngine:
     def close(self) -> None:
         self._listener_thread.join()
         if self.send_type == "PUT_ASYNC":
+            self._send_thread.join()
             self._pending_check_thread.join()
         if self._ping_thread is not None:
             self._ping_thread.join()