[WIP] add realted ut for migration rollback feature

[wulemao]

What type of PR is this?

/kind failing-test

What this PR does / why we need it:

add realted ut for migration rollback feature

Which issue(s) this PR fixes:

Fixes part of #5380

Special notes for your reviewer:

！！！need rebasing upon #5626, waiting for it to be merged

Does this PR introduce a user-facing change?:

[karmada-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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Needs approval from an approver in each of these files:

• pkg/karmadactl/OWNERS
• pkg/util/OWNERS

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[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 6.08108% with 139 lines in your changes missing coverage. Please review.

Project coverage is 35.11%. Comparing base (eaa3452) to head (ba315a3).
Report is 20 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/karmadactl/unregister/unregister.go	7.56%	110 Missing ⚠️
pkg/karmadactl/util/cluster.go	0.00%	22 Missing ⚠️
pkg/util/secret.go	0.00%	5 Missing ⚠️
pkg/karmadactl/karmadactl.go	0.00%	1 Missing ⚠️
pkg/karmadactl/unjoin/unjoin.go	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5628      +/-   ##
==========================================
+ Coverage   35.01%   35.11%   +0.10%     
==========================================
  Files         645      647       +2     
  Lines       44861    44994     +133     
==========================================
+ Hits        15708    15800      +92     
- Misses      27938    27963      +25     
- Partials     1215     1231      +16     

Flag	Coverage Δ
unittests	35.11% <6.08%> (+0.10%)	⬆️

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