add some uts and some optimization

[nicole-lihui]

• add uts
• optimize http code return is hard code

[mergify]

Welcome to the Merbridge OpenSource Community!👏

We're delighted to have you onboard 💘

[codecov-commenter]

Codecov Report

Merging #192 (a72386c) into main (a47ce70) will increase coverage by 20.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##             main     #192       +/-   ##
===========================================
+ Coverage   17.11%   37.12%   +20.00%     
===========================================
  Files           5        5               
  Lines         368      369        +1     
===========================================
+ Hits           63      137       +74     
+ Misses        295      218       -77     
- Partials       10       14        +4     

Flag	Coverage Δ
unittests	37.12% <100.00%> (+20.00%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
controller/localip/localip.go	31.05% <100.00%> (+7.24%)	⬆️
pkg/cniplugin/plugin.go	36.52% <0.00%> (+26.08%)	⬆️
pkg/cniplugin/kube.go	62.50% <0.00%> (+62.50%)	⬆️

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[kebe7jun]

Thanks!