Supplementary unit test #2177 team6

[thinkerleolee]

What is the purpose of the change

Resolve #2177.

Brief changelog

The following branches have been Unit Tested:
org.apache.dubbo.registry.support.AbstractRegistry#notify
org.apache.dubbo.registry.support.AbstractRegistry#lookup
org.apache.dubbo.registry.support.AbstractRegistry#getCacheUrl
org.apache.dubbo.registry.support.AbstractRegistry#toString
org.apache.dubbo.registry.support.AbstractRegistry#getCacheFile
org.apache.dubbo.registry.support.AbstractRegistry#getCacheProperties
org.apache.dubbo.registry.support.AbstractRegistry#getLastCacheChange
org.apache.dubbo.registry.support.AbstractRegistry#filterEmpty
org.apache.dubbo.registry.support.AbstractRegistry#setUrl
org.apache.dubbo.registry.support.AbstractRegistry#destory

BaiJi training camp 269 Team No.6, Alibaba-Inc.

Verifying this change

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