- [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).
*     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.dubbo.registry.integration;
import org.apache.dubbo.common.Constants;
import org.apache.dubbo.common.URL;
import org.apache.dubbo.common.Version;
import org.apache.dubbo.common.extension.ExtensionLoader;
import org.apache.dubbo.common.logger.Logger;
import org.apache.dubbo.common.logger.LoggerFactory;
import org.apache.dubbo.common.utils.Assert;
import org.apache.dubbo.common.utils.NetUtils;
import org.apache.dubbo.common.utils.StringUtils;
import org.apache.dubbo.common.utils.UrlUtils;
import org.apache.dubbo.common.utils.CollectionUtils;
import org.apache.dubbo.configcenter.DynamicConfiguration;
import org.apache.dubbo.registry.NotifyListener;
import org.apache.dubbo.registry.Registry;
import org.apache.dubbo.rpc.Invocation;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.Protocol;
import org.apache.dubbo.rpc.RpcException;
import org.apache.dubbo.rpc.cluster.Cluster;
import org.apache.dubbo.rpc.cluster.Configurator;
import org.apache.dubbo.rpc.cluster.Router;