[Bugfix] Fix colocate-async sleep admission race and deliver AR abort tokens (#6367)

Signed-off-by: knlnguyen1802 <knlnguyen1802@gmail.com>
Signed-off-by: Cursor <cursoragent@cursor.com>
Signed-off-by: Samit <285365963@qq.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Samit <285365963@qq.com>

tests/engine/test_async_omni_engine_abort_ack.py

@@ -67,7 +67,8 @@ def test_abort_async_waits_for_ack(mocker: MockerFixture):
         assert not task.done()
 
         rpc_q.put(AbortResultMessage(rpc_id="abort-rpc-1", success=True))
-        await task
+        result = await task
+        assert result == []
 
     try:
         asyncio.run(_run())