Automated cherry pick of #4371: fix(util/proxy): fix tls.config when secret.spec.caBundle is

[XiShanYongYe-Chang]

Cherry pick of #4371 on release-1.8.
#4371: fix(util/proxy): fix tls.config when secret.spec.caBundle is
For details on the cherry pick process, see the cherry pick requests page.

`karmadactl`: Fixed return err in case of `secret.spec.caBundle` is nil

[codecov-commenter]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (6bdcd9c) 51.79% compared to head (d1c7eea) 51.78%.

Files	Patch %	Lines
pkg/util/proxy/proxy.go	0.00%	5 Missing ⚠️

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Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.8    #4391      +/-   ##
===============================================
- Coverage        51.79%   51.78%   -0.02%     
===============================================
  Files              243      243              
  Lines            24112    24110       -2     
===============================================
- Hits             12490    12485       -5     
- Misses           10942    10944       +2     
- Partials           680      681       +1     

Flag	Coverage Δ
unittests	51.78% <0.00%> (-0.02%)	⬇️

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[whitewindmills]

/lgtm
/approve

[karmada-bot]

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This pull-request has been approved by: whitewindmills

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