- [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).
import static org.apache.dubbo.common.Constants.CONSUMERS_CATEGORY;
import static org.apache.dubbo.common.Constants.CONSUMER_PROTOCOL;
import static org.apache.dubbo.common.Constants.DEFAULT_DIRECTORY;
import static org.apache.dubbo.common.Constants.DEFAULT_REGISTER_CONSUMER_KEYS;
import static org.apache.dubbo.common.Constants.DEFAULT_REGISTER_PROVIDER_KEYS;
import static org.apache.dubbo.common.Constants.DEFAULT_REGISTRY;
import static org.apache.dubbo.common.Constants.EXPORT_KEY;
import static org.apache.dubbo.common.Constants.EXTRA_KEYS_KEY;
import static org.apache.dubbo.common.Constants.HIDE_KEY_PREFIX;
import static org.apache.dubbo.common.Constants.INTERFACES;
import static org.apache.dubbo.common.Constants.METHODS_KEY;
import static org.apache.dubbo.common.Constants.MONITOR_KEY;
import static org.apache.dubbo.common.Constants.OVERRIDE_PROTOCOL;
import static org.apache.dubbo.common.Constants.PROVIDERS_CATEGORY;
import static org.apache.dubbo.common.Constants.PROVIDER_PROTOCOL;
import static org.apache.dubbo.common.Constants.QOS_ENABLE;
import static org.apache.dubbo.common.Constants.QOS_PORT;
import static org.apache.dubbo.common.Constants.REFER_KEY;
import static org.apache.dubbo.common.Constants.REGISTER_IP_KEY;
import static org.apache.dubbo.common.Constants.REGISTER_KEY;
import static org.apache.dubbo.common.Constants.REGISTRY_KEY;
import static org.apache.dubbo.common.Constants.REGISTRY_PROTOCOL;
import static org.apache.dubbo.common.Constants.ROUTERS_CATEGORY;
import static org.apache.dubbo.common.Constants.SIMPLIFIED_KEY;
import static org.apache.dubbo.common.Constants.VALIDATION_KEY;
import static org.apache.dubbo.common.utils.UrlUtils.classifyUrls;
/**
 * RegistryProtocol
 */
public class RegistryProtocol implements Protocol {