- [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).
final Invoker<?> invoker;
            if (originInvoker instanceof InvokerDelegate) {
                invoker = ((InvokerDelegate<?>) originInvoker).getInvoker();
            } else {
                invoker = originInvoker;
            }
            
            URL originUrl = RegistryProtocol.this.getProviderUrl(invoker);
            String key = getCacheKey(originInvoker);
            ExporterChangeableWrapper<?> exporter = bounds.get(key);
            if (exporter == null) {
                logger.warn(new IllegalStateException("error state, exporter should not be null"));
                return;
            }
            
            URL currentUrl = exporter.getInvoker().getUrl();
            
            URL newUrl = getConfigedInvokerUrl(configurators, originUrl);
            newUrl = getConfigedInvokerUrl(serviceConfigurationListeners.get(originUrl.getServiceKey())
                    .getConfigurators(), newUrl);
            newUrl = getConfigedInvokerUrl(providerConfigurationListener.getConfigurators(), newUrl);
            if (!currentUrl.equals(newUrl)) {
                RegistryProtocol.this.reExport(originInvoker, newUrl);
                logger.info("exported provider url changed, origin url: " + originUrl +
                        ", old export url: " + currentUrl + ", new export url: " + newUrl);
            }
        }
        private List<URL> getMatchedUrls(List<URL> configuratorUrls, URL currentSubscribe) {
            List<URL> result = new ArrayList<URL>();
            for (URL url : configuratorUrls) {