### Environment

* Dubbo version: 3.1.0
* Operating System version: xxx
* Java version: 1.8
* Istio version: 1.13.2

### Steps to reproduce this issue

1. 运行Istio+proxyless [demo程序 ](https://github.com/apache/dubbo-samples/tree/master/dubbo-samples-xds )，启动后consumer能正常访问provider。
2. 扩大provider副本数为2， consumer无法感知到新增的provider节点，新增的provider节点也没有收到consumer的请求。
3. 删除provider对应的k8s service（取消服务注册），consumer没有感知到服务变化，仍然可以继续调用provider。
4. 恢复provider service后，重启consumer实例，consumer才可以正常发现2个provider节点。

resourceNames = resourceNames == null ? Collections.emptySet() : resourceNames;
        
        requestParam.put(request, resourceNames);
        
        consumer.accept(getResource(resourceNames));
        
        StreamObserver<DiscoveryRequest> requestObserver = xdsChannel.createDeltaDiscoveryRequest(new ResponseObserver(request));
        requestObserverMap.put(request, requestObserver);
        ScheduledFuture<?> scheduledFuture = pollingExecutor.scheduleAtFixedRate(() -> {
            try {
                
                Set<String> names = requestParam.get(request);
                
                CompletableFuture<T> future = new CompletableFuture<>();
                streamResult.put(request, future);
                
                StreamObserver<DiscoveryRequest> observer = requestObserverMap.get(request);
                
                observer.onNext(buildDiscoveryRequest(names));
                try {
                    
                    consumer.accept(future.get());
                } catch (InterruptedException | ExecutionException e) {
                    logger.error("Error occur when request control panel.");
                } finally {
                    
                    
                    
                    streamResult.remove(request);
                }