[P/D][BugFix] Fix layerwise P/D request_id error (#6360)

### What this PR does / why we need it?
Fix layerwise Connector P/D request_id error, due to vllm pr:
https://github.com/vllm-project/vllm/pull/27987, which will add a random
suffix to request_id in EngineCore.

- vLLM version: v0.14.1
- vLLM main:
dc917cceb8
---------
Signed-off-by: nwpu-zxr <zhouxuerong2@huawei.com>

tests/ut/kv_connector/test_mooncake_layerwise_connector.py

@@ -240,6 +240,7 @@ class TestKVCacheRecvingLayerThread(unittest.TestCase):
 
         with th.lock:
             th.task_tracker["reqX"] = 0
+            th.request_map["reqX"] = "reqX"
 
         th.update_task("reqX")
         with th.lock:
@@ -313,6 +314,7 @@ class TestKVCacheRecvingLayerThread(unittest.TestCase):
 
         with th.lock:
             th.task_tracker["reqA"] = 0
+            th.request_map["reqA"] = "reqA"
 
         with self.assertRaises(SystemExit):
             th.run()
@@ -386,6 +388,7 @@ class TestKVCacheRecvingLayerThread(unittest.TestCase):
                                        ready_event=self.ready_event)
         with th.lock:
             th.task_tracker["reqB"] = 0
+            th.request_map["reqB"] = "reqB"
         with self.assertRaises(SystemExit):
             th.run()