- [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

private transient volatile boolean initialized;
    /**
     * whether this ReferenceConfig has been destroyed
     */
    private transient volatile boolean destroyed;
    @SuppressWarnings("unused")
    private final Object finalizerGuardian = new Object() {
        @Override
        protected void finalize() throws Throwable {
            super.finalize();
            if (!ReferenceConfig.this.destroyed) {
                logger.warn("ReferenceConfig(" + url + ") is not DESTROYED when FINALIZE");
                /* don't destroy for now
                try {
                    ReferenceConfig.this.destroy();
                } catch (Throwable t) {
                        logger.warn("Unexpected err when destroy invoker of ReferenceConfig(" + url + ") in finalize method!", t);
                }
                */
            }
        }
    };
    public ReferenceConfig() {
    }
    public ReferenceConfig(Reference reference) {
        appendAnnotation(Reference.class, reference);
        setMethods(MethodConfig.constructMethodConfig(reference.methods()));
    }
    public URL toUrl() {
        return urls.isEmpty() ? null : urls.iterator().next();