[Bugfix][V1][P/D]Fix the uneven polling issue in the toy proxy for P2pNcclConnector (#21819)

Signed-off-by: Abatom <abzhonghua@gmail.com>

examples/online_serving/disaggregated_serving_p2p_nccl_xpyd/disagg_proxy_p2p_nccl_xpyd.py

@@ -46,7 +46,7 @@ def _listen_for_register(poller, router_socket):
                 global prefill_instances
                 global prefill_cv
                 with prefill_cv:
-                    node = prefill_instances.pop(data["http_address"], None)
+                    node = prefill_instances.get(data["http_address"], None)
                     prefill_instances[data["http_address"]] = (
                         data["zmq_address"],
                         time.time() + DEFAULT_PING_SECONDS,
@@ -57,7 +57,7 @@ def _listen_for_register(poller, router_socket):
                 global decode_instances
                 global decode_cv
                 with decode_cv:
-                    node = decode_instances.pop(data["http_address"], None)
+                    node = decode_instances.get(data["http_address"], None)
                     decode_instances[data["http_address"]] = (
                         data["zmq_address"],
                         time.time() + DEFAULT_PING_SECONDS,
@@ -69,6 +69,7 @@ def _listen_for_register(poller, router_socket):
                     remote_address,
                     data,
                 )
+                return
 
             if node is None:
                 print(f"🔵Add [HTTP:{data['http_address']}, ZMQ:{data['zmq_address']}]")