### 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。

import org.apache.dubbo.common.logger.LoggerFactory;
import org.apache.dubbo.common.utils.NamedThreadFactory;
import org.apache.dubbo.registry.xds.util.XdsChannel;
import io.envoyproxy.envoy.config.core.v3.Node;
import io.envoyproxy.envoy.service.discovery.v3.DiscoveryRequest;
import io.envoyproxy.envoy.service.discovery.v3.DiscoveryResponse;
import io.grpc.stub.StreamObserver;
import java.util.Collections;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.Consumer;
public abstract class AbstractProtocol<T, S extends DeltaResource<T>> implements XdsProtocol<T> {
    private static final Logger logger = LoggerFactory.getLogger(AbstractProtocol.class);
    protected final XdsChannel xdsChannel;
    protected final Node node;
    /**
     * Store Request Parameter ( resourceNames )
     * K - requestId, V - resourceNames
     */
    protected final Map<Long, Set<String>> requestParam = new ConcurrentHashMap<>();
    /**
     * Store ADS Request Observer ( StreamObserver in Streaming Request )