[V1][BugFix] Fix engine core client shutdown hangs (#13298)

Even though ZMQ context.destroy() is meant to close open sockets before terminating the context, it appears to be necessary to do this explicitly or else it can hang in the context.term() method.

Close zmq sockets explicitly before terminating context, make shutdown of client resource more robust, shut down engine core process prior to terminating zmq context.

Signed-off-by: Nick Hill <nhill@redhat.com>

tests/v1/engine/test_engine_core_client.py

@@ -3,7 +3,6 @@
 import asyncio
 import time
 import uuid
-from contextlib import ExitStack
 from typing import Dict, List, Optional
 
 import pytest
@@ -178,7 +177,7 @@ def test_engine_core_client(monkeypatch, multiprocessing_mode: bool):
 @pytest.mark.asyncio(loop_scope="function")
 async def test_engine_core_client_asyncio(monkeypatch):
 
-    with monkeypatch.context() as m, ExitStack() as after:
+    with monkeypatch.context() as m:
         m.setenv("VLLM_USE_V1", "1")
 
         # Monkey-patch core engine utility function to test.
@@ -195,7 +194,6 @@ async def test_engine_core_client_asyncio(monkeypatch):
             executor_class=executor_class,
             log_stats=True,
         )
-        after.callback(client.shutdown)
 
         MAX_TOKENS = 20
         params = SamplingParams(max_tokens=MAX_TOKENS)