[BugFix] Avoid error traceback in logs when V1 LLM terminates

[njhill]

Introduced by #13060.

Exception in thread Thread-3 (process_outputs_socket):
Traceback (most recent call last):
  File "/data/woosuk/miniconda3/envs/vllm-py311/lib/python3.11/threading.py", line 1045, in _bootstrap_inner
    self.run()
  File "/data/woosuk/miniconda3/envs/vllm-py311/lib/python3.11/threading.py", line 982, in run
    self._target(*self._args, **self._kwargs)
  File "/data/woosuk/workspace/vllm/vllm/v1/engine/core_client.py", line 256, in process_outputs_socket
    (frame, ) = output_socket.recv_multipart(copy=False)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/data/woosuk/miniconda3/envs/vllm-py311/lib/python3.11/site-packages/zmq/sugar/socket.py", line 808, in recv_multipart
    parts = [self.recv(flags, copy=copy, track=track)]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "_zmq.py", line 1156, in zmq.backend.cython._zmq.Socket.recv
  File "_zmq.py", line 1193, in zmq.backend.cython._zmq.Socket.recv
  File "_zmq.py", line 1258, in zmq.backend.cython._zmq._recv_frame
  File "_zmq.py", line 175, in zmq.backend.cython._zmq._check_rc
zmq.error.ContextTerminated: Context was terminated

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[WoosukKwon]

Works on my machine!