[P/D] [bugfix] add get_kv_connector_handshake_metadata func for 0.11.2 (#4567)

### What this PR does / why we need it?
add get_kv_connector_handshake_metadata func for 0.11.2


Signed-off-by: liziyu <liziyu16@huawei.com>

Author: liziyu179

vllm_ascend/worker/worker_v1.py

@@ -369,6 +369,9 @@ def _warm_up_atb(self):
     def get_model(self) -> nn.Module:
         return self.model_runner.get_model()
 
+    def get_kv_connector_handshake_metadata(self) -> Optional[dict]:
+        return None
+
     def get_kv_cache_spec(self) -> dict[str, KVCacheSpec]:
         return self.model_runner.get_kv_cache_spec()