remove insecureSkipTLSVerify in UT test

[chaosi-zju]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Backupground: insecureSkipTLSVerify=true means prohibit clientside from verifing the cert of serverside, this is an unsafe configuration, we can avoid unnecessary unsafe configurations.

This PR mainly aims to remove insecureSkipTLSVerify in UT.

Which issue(s) this PR fixes:

part of #4024

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

none

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.01% ⚠️

Comparison is base (244c73c) 53.82% compared to head (19c63fc) 53.81%.
Report is 2 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4062      +/-   ##
==========================================
- Coverage   53.82%   53.81%   -0.01%     
==========================================
  Files         231      231              
  Lines       23013    23013              
==========================================
- Hits        12386    12385       -1     
- Misses       9954     9955       +1     
  Partials      673      673              

Flag	Coverage Δ
unittests	53.81% <ø> (-0.01%)	⬇️

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see 1 file with indirect coverage changes

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[XiShanYongYe-Chang]

Thanks
/lgtm

[RainbowMango]

/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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