Test_imageToCriImage

[KevinLeung611]

Ⅰ. Describe what this PR did

add unit-test for imageToCriImage

Ⅱ. Does this pull request fix one issue?

fix issue #1914

Ⅲ. Describe how you did it

1. understand what the imageToImage method does.
2. add some args that the imageToImage method needs
3. go test

Ⅳ. Describe how to verify it

verify User, including "", numeric string, string, contains ":"
verify Uid, if user is numeric string, whether the uid is correct
verify ID, numeric string and common string
verify RepoTags, common string
verify RepoDigests, common string
verify Size_, common int64

Ⅴ. Special notes for reviews

[CLAassistant]

Thank you for your submission, we really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

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[pouchrobot]

We found this is your first time to contribute to Pouch, @KevinLeung-nice
👏 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! 🍻

[pouchrobot]

@KevinLeung-nice Thanks for your contribution. 🍻
Please sign off in each of your commits.

[codecov-io]

Codecov Report

Merging #1990 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1990      +/-   ##
==========================================
+ Coverage   63.31%   63.36%   +0.04%     
==========================================
  Files         200      200              
  Lines       15522    15522              
==========================================
+ Hits         9828     9835       +7     
+ Misses       4455     4448       -7     
  Partials     1239     1239

Flag	Coverage Δ
#criv1alpha1test	33.82% <ø> (-0.03%)	⬇️
#criv1alpha2test	34.28% <ø> (ø)	⬆️
#integrationtest	38.44% <ø> (ø)	⬆️
#unittest	21.26% <ø> (+0.4%)	⬆️

Impacted Files	Coverage Δ
ctrd/watch.go	72.72% <0%> (-3.04%)	⬇️
cri/v1alpha1/cri_utils.go	75.89% <0%> (+1.6%)	⬆️