chore: remove refs to deprecated io/ioutil

[testwill]

Ⅰ. Describe what this PR does

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how to verify it

Ⅳ. Special notes for reviews

[zmberg]

@testwill You should exec 'File is not gofmt-ed with -s (gofmt)' in file checker.go

[codecov-commenter]

Codecov Report

Merging #1404 (0c5fd8b) into master (a477df8) will increase coverage by 0.06%.
Report is 1 commits behind head on master.
The diff coverage is n/a.

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@@            Coverage Diff             @@
##           master    #1404      +/-   ##
==========================================
+ Coverage   48.25%   48.31%   +0.06%     
==========================================
  Files         152      152              
  Lines       21469    21469              
==========================================
+ Hits        10359    10373      +14     
+ Misses       9973     9963      -10     
+ Partials     1137     1133       -4     

Flag	Coverage Δ
unittests	48.31% <ø> (+0.06%)	⬆️

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see 3 files with indirect coverage changes

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[zmberg]

/lgtm

[zmberg]

/approve

[kruise-bot]

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