### 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" />`
```

}
    @Parameter(excluded = true)
    public String getHostname() {
        if (hostname == null) {
            try {
                hostname = InetAddress.getLocalHost().getHostName();
            } catch (UnknownHostException e) {
                LOGGER.warn("Failed to get the hostname of current instance.", e);
                hostname = "UNKNOWN";
            }
        }
        return hostname;
    }
    @Override
    @Parameter(excluded = true)
    public boolean isValid() {
        return !StringUtils.isEmpty(name);
    }
    public String getMetadataType() {
        return metadataType;
    }
    public void setMetadataType(String metadataType) {
        this.metadataType = metadataType;
    }
    public Boolean getRegisterConsumer() {
        return registerConsumer;
    }
    public void setRegisterConsumer(Boolean registerConsumer) {
        this.registerConsumer = registerConsumer;
    }