- [x] I have searched the [issues](https://github.com/apache/incubator-dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/incubator-dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.0
* Operating System version: mac
* Java version: 1.8

### Steps to reproduce this issue

1.  `AbstractClient#initConnectStatusCheckCommand` set break point at `  !isConnected()`.
2. `AbstractClient#close()` set break point here.    
3.  start client first, start provider and then shutdown provider gracefully , let method `AbstractClient.close()` be executed. Then select step `1` and trigger the thread to execute `!isConnected`, here will always try to connect the offline machine.

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

What do you expected from the above steps？

When the server goes offline, the client will not reconnect the offline machine.

### Actual Result

What actually happens?

The client reconnects the offline machine every 2 seconds and causes a large number of arp packets(because ip is recycled and not available now).
private final Invoker<T> originInvoker;
        private Exporter<T> exporter;
        private URL subscribeUrl;
        private URL registerUrl;
        public ExporterChangeableWrapper(Exporter<T> exporter, Invoker<T> originInvoker) {
            this.exporter = exporter;
            this.originInvoker = originInvoker;
        }
        public Invoker<T> getOriginInvoker() {
            return originInvoker;
        }
        @Override
        public Invoker<T> getInvoker() {
            return exporter.getInvoker();
        }
        public void setExporter(Exporter<T> exporter) {
            this.exporter = exporter;
        }
        @Override
        public void unexport() {
            String key = getCacheKey(this.originInvoker);
            bounds.remove(key);
            Registry registry = RegistryProtocol.INSTANCE.getRegistry(originInvoker);
            try {
                registry.unregister(registerUrl);
            } catch (Throwable t) {
                logger.warn(t.getMessage(), t);
            }
            try {
                NotifyListener listener = RegistryProtocol.INSTANCE.overrideListeners.remove(subscribeUrl);