fix ValidateCPUPeroid

[mengjiahao]

Ⅰ. Describe what this PR did

#1637 : add unit-test for apis/opts/cpu.go ValidateCPUPeroid

Ⅱ. Does this pull request fix one issue?

NONE

Ⅲ. Describe how you did it

NONE

Ⅳ. Describe how to verify it

NONE

Ⅴ. Special notes for reviews

NONE

[CLAassistant]

All committers have signed the CLA.

[pouchrobot]

We found this is your first time to contribute to Pouch, @mengjiahao
👏 We really appreciate it.
Just remind that you have read the contribution guide: https://github.com/alibaba/pouch/blob/master/CONTRIBUTING.md
If you didn't, you should do that first. If done, welcome again and please enjoy hacking! 🍻

[codecov-io]

Codecov Report

Merging #1655 into master will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1655      +/-   ##
==========================================
+ Coverage   41.16%   41.19%   +0.03%     
==========================================
  Files         274      274              
  Lines       18091    18089       -2     
==========================================
+ Hits         7447     7452       +5     
+ Misses       9729     9724       -5     
+ Partials      915      913       -2

Impacted Files	Coverage Δ
ctrd/image.go	75.27% <0%> (-2.75%)	⬇️
daemon/mgr/system.go	75% <0%> (-1.73%)	⬇️
cli/common_flags.go	0% <0%> (ø)	⬆️
cli/container.go	0% <0%> (ø)	⬆️
daemon/mgr/container.go	50.23% <0%> (+0.15%)	⬆️
daemon/logger/jsonfile/utils.go	73.17% <0%> (+1.62%)	⬆️
apis/server/utils.go	66.66% <0%> (+4.76%)	⬆️
apis/opts/cpu.go	50% <0%> (+50%)	⬆️

[pouchrobot]

@mengjiahao Thanks for your contribution. 🍻
Please sign off in each of your commits.