### Environment

* Dubbo version: 2.7.5
* Operating System version: win10 or centos7
* Java version: 1.8.0
* Zookeeper version: 3.5.6

### Steps to reproduce this issue
My previous dubbo service version was 2.7.3. Today, I upgraded to 2.7.5. I found that the metadata can't be displayed all the time. The dubbo service registry in zookeeper, but zookeeper not /dubbo/metadata node path view.  If I switch back to 2.7.3 and 2.7.4.1, it can be displayed. Are there any bugs? I need help~~

xml-config:
`<dubbo:metadata-report address="zookeeper://192.168.11.100:2181?backup=192.168.11.105:2181" />`
```

String DUBBO = "dubbo";
    String PROVIDER = "provider";
    String CONSUMER = "consumer";
    String APPLICATION_KEY = "application";
    String REMOTE_APPLICATION_KEY = "remote.application";
    String ENABLED_KEY = "enabled";
    String DISABLED_KEY = "disabled";
    String DUBBO_PROPERTIES_KEY = "dubbo.properties.file";
    String DEFAULT_DUBBO_PROPERTIES = "dubbo.properties";
    String ANY_VALUE = "*";
    String COMMA_SEPARATOR = ",";
    String DOT_SEPARATOR = ".";