chore: use errors.Is to check for a specific error

[Fish-pro]

Signed-off-by: Fish-pro zechun.chen@daocloud.io

What this PR does / why we need it:

Comparing with == will fail on wrapped errors. Use errors.Is to check for a specific error

Which issue(s) this PR fixes (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):
Fixes #

Special notes for your reviewer:

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 53.19%. Comparing base (a30d288) to head (7448f4b).
Report is 721 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/audit/manager.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2483      +/-   ##
==========================================
- Coverage   53.22%   53.19%   -0.03%     
==========================================
  Files         116      116              
  Lines       10270    10270              
==========================================
- Hits         5466     5463       -3     
- Misses       4380     4382       +2     
- Partials      424      425       +1     

Flag	Coverage Δ
unittests	53.19% <33.33%> (-0.03%)	⬇️

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[sozercan]

Thank you! LGTM

[maxsmythe]

Thank you! LGTM