- [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 Class<?> getInterfaceClass() {
        if (interfaceClass != null) {
            return interfaceClass;
        }
        if (isGeneric()
                || (getConsumer() != null && getConsumer().isGeneric())) {
            return GenericService.class;
        }
        try {
            if (interfaceName != null && interfaceName.length() > 0) {
                this.interfaceClass = Class.forName(interfaceName, true, ClassUtils.getClassLoader());
            }
        } catch (ClassNotFoundException t) {
            throw new IllegalStateException(t.getMessage(), t);
        }
        return interfaceClass;
    }
    /**
     * @param interfaceClass
     * @see #setInterface(Class)
     * @deprecated
     */
    @Deprecated
    public void setInterfaceClass(Class<?> interfaceClass) {
        setInterface(interfaceClass);
    }
    public String getInterface() {
        return interfaceName;
    }