Revert interceptor all ui problem

[KomachiSion]

Please do not create a Pull Request without creating an issue first.

What is the purpose of the change

For #4701.

Found if interceptor all un register api, ui will be interceptor too.

so only add '/' support in methodCache first.

Brief changelog

XX

Verifying this change

XXXX

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[lzp0412]

LGTM

[yimao]

需要注意的是 TAG 1.4.1 (Jan 15, 2021) 并不包括 #4708 这次提交，用户依然需要基于1.4.1 tag 手动合并 #4708 改动，然后重新打包部署才能解决首页访问 404 的问题。

[zxhans]

不单是首页，client的jar 1.4.1里面，contextPath=/nacos 这个contextPath整个都丢了，变成了“”