Fix consumer refresh issue in instance registration cache.

What is the purpose of the change

When configuring metadataType=remote on the application side, there is no MetadataService service export, and the incorrect call of dubbo admin causes many exceptions on the application side.

java.io.IOException: Service org.apache.dubbo.metadata.MetadataService with version 1.0.0 not found, invocation rejected.

应用配置metadataType=remote的时候，dubbo-admin这里的MetadataService metadataService = MetadataUtils.referProxy(instance).getProxy(); 失败调用会对应用侧产生大量异常日志。另外，不清楚这里定时刷新的作用是什么？从代码上看仅仅只是触发了一次metadataService.getSubscribedURLs();调用，对subscribedCache也没有什么操作.

Brief changelog

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apache / dubbo-admin