[main][Bugix] fix kv pcp+pooling+pd separation bug (#6153)

### What this PR does / why we need it?
Rectify the problem that the pcp and pd separation and kv pooling
scenario.

In the pooling scenario, multi_nodes_meta_mapping is empty. As a result,
an error is reported when the remote_host information is obtained
through the get_remote_port_send_num method.

### Does this PR introduce _any_ user-facing change?
No

- vLLM version: v0.13.0
- vLLM main:
d68209402d

Signed-off-by: weiguihua2 <weiguihua2@huawei.com>

vllm_ascend/distributed/kv_transfer/kv_p2p/mooncake_connector.py

@@ -1472,8 +1472,11 @@ class MooncakeConnectorWorker:
         ) -> dict[int, RemotePortInfo]:
             remote_port_send_num: dict[int, RemotePortInfo] = {}
             for port in range(self._prefill_tp_size * meta.remote_pcp_size):
-                remote_host = str(meta.remote_multi_nodes_meta_mapping[str(
-                    port)]['host'])
+                remote_host_info = meta.remote_multi_nodes_meta_mapping.get(str(port), None)
+                if remote_host_info is None:
+                    remote_host = meta.remote_host
+                else:
+                    remote_host = remote_host_info['host']
                 remote_port_send_num[meta.remote_port + port] = {
                     'num': 0,
                     'host': remote_host