[BugFix] make sure socket close (vllm-project#15875)

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

Author: yihong0618

vllm/entrypoints/openai/api_server.py

@@ -1098,9 +1098,10 @@ def _listen_addr(a: str) -> str:
         )
 
     # NB: Await server shutdown only after the backend context is exited
-    await shutdown_task
-
-    sock.close()
+    try:
+        await shutdown_task
+    finally:
+        sock.close()
 
 
 if __name__ == "__main__":