- [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

public void setInterface(String interfaceName) {
        this.interfaceName = interfaceName;
        if (StringUtils.isEmpty(id)) {
            id = interfaceName;
        }
    }
    public void setInterface(Class<?> interfaceClass) {
        if (interfaceClass != null && !interfaceClass.isInterface()) {
            throw new IllegalStateException("The interface class " + interfaceClass + " is not a interface!");
        }
        this.interfaceClass = interfaceClass;
        setInterface(interfaceClass == null ? null : interfaceClass.getName());
    }
    public String getClient() {
        return client;
    }
    public void setClient(String client) {
        checkName(Constants.CLIENT_KEY, client);
        this.client = client;
    }
    @Parameter(excluded = true)
    public String getUrl() {
        return url;
    }
    public void setUrl(String url) {
        this.url = url;
    }
    public List<MethodConfig> getMethods() {
        return methods;
    }