- [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: Windows7
* Java version: jdk8

### Steps to reproduce this issue

1. stop dubbo service
2. dubbo client set checked = true.  do get cudbbo client for times.
3. the size of list field [urls] in ReferenceConfig wil increase

Pls. provide [GitHub address] to reproduce this issue.
(project)[https://github.com/vio-lin/incubator-dubbo/tree/error-situation]  
run java file 
 incubator-dubbo\dubbo-demo\dubbo-demo-xml\dubbo-demo-xml-consumer\src\main\java\org\apache\dubbo\demo\consumer\Application.java
### Expected Result
the [urls] in ReferenceConfig will be updated.

### Actual Result
the avalidable registery urls be add to [urls] in ReferenceConfig

import static org.apache.dubbo.common.constants.CommonConstants.INTERFACE_KEY;
import static org.apache.dubbo.common.constants.CommonConstants.LOCALHOST_VALUE;
import static org.apache.dubbo.common.constants.CommonConstants.METHODS_KEY;
import static org.apache.dubbo.common.constants.CommonConstants.REVISION_KEY;
import static org.apache.dubbo.common.constants.CommonConstants.SEMICOLON_SPLIT_PATTERN;
import static org.apache.dubbo.common.constants.CommonConstants.SIDE_KEY;
import static org.apache.dubbo.common.constants.ConfigConstants.CLUSTER_KEY;
import static org.apache.dubbo.config.Constants.DUBBO_IP_TO_REGISTRY;
import static org.apache.dubbo.rpc.cluster.Constants.REFER_KEY;
import static org.apache.dubbo.registry.Constants.REGISTER_IP_KEY;
import static org.apache.dubbo.common.constants.CommonConstants.MONITOR_KEY;
import static org.apache.dubbo.registry.Constants.CONSUMER_PROTOCOL;
import static org.apache.dubbo.common.constants.RegistryConstants.REGISTRY_PROTOCOL;
import static org.apache.dubbo.rpc.Constants.LOCAL_PROTOCOL;
import static org.apache.dubbo.common.utils.NetUtils.isInvalidLocalHost;
/**
 * ReferenceConfig
 *
 * @export
 */
public class ReferenceConfig<T> extends AbstractReferenceConfig {
    private static final long serialVersionUID = -5864351140409987595L;
    /**
     * The {@link Protocol} implementation with adaptive functionality,it will be different in different scenarios.
     * A particular {@link Protocol} implementation is determined by the protocol attribute in the {@link URL}.
     * For example:
     *
     * <li>when the url is registry://224.5.6.7:1234/org.apache.dubbo.registry.RegistryService?application=dubbo-sample,
     * then the protocol is <b>RegistryProtocol</b></li>
     *