test: add unit test to getSELinuxSecurityOpts

[MarkLux]

Ⅰ. Describe what this PR did

add the unit test for criutils getSELinuxSecurityOpts() function, with input cases check.

Ⅱ. Does this pull request fix one issue?

fixes #1912

Ⅲ. Describe how you did it

add normal and nil input test cases to verify the function output

Ⅳ. Describe how to verify it

run go test -v run getSELinuxSecurityOpts in package v1alpha1

Ⅴ. Special notes for reviews

maybe it's better to further check the format of SELinux Options

[CLAassistant]

All committers have signed the CLA.

[pouchrobot]

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

[pouchrobot]

We found this is your first time to contribute to Pouch, @MarkLux
👏 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 #1939 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1939      +/-   ##
==========================================
+ Coverage    63.3%   63.35%   +0.05%     
==========================================
  Files         200      200              
  Lines       15521    15521              
==========================================
+ Hits         9825     9833       +8     
+ Misses       4456     4447       -9     
- Partials     1240     1241       +1

Flag	Coverage Δ
#criv1alpha1test	33.76% <ø> (+0.01%)	⬆️
#criv1alpha2test	34.23% <ø> (-0.09%)	⬇️
#integrationtest	38.4% <ø> (ø)	⬆️
#unittest	20.99% <ø> (+0.13%)	⬆️

Impacted Files	Coverage Δ
cri/stream/portforward/httpstream.go	69.16% <0%> (-6.67%)	⬇️
cri/stream/runtime.go	71.01% <0%> (-2.9%)	⬇️
daemon/logger/jsonfile/utils.go	73.17% <0%> (+1.62%)	⬆️
cri/v1alpha1/cri_utils.go	77.14% <0%> (+2.85%)	⬆️