chore: fix to update one pod at a time in a rolling update

[leon-inf]

cherry picked from commit c620878

[apecloud-bot]

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[leon-inf]

/nopick

[leon-inf]

/approve

[codecov]

Codecov Report

❌ Patch coverage is 43.85965% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.02%. Comparing base (ba2ccb5) to head (71105fc).

Files with missing lines	Patch %	Lines
pkg/controller/instanceset/reconciler_update.go	40.74%	23 Missing and 9 partials ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.0    #9810      +/-   ##
===============================================
+ Coverage        59.94%   60.02%   +0.07%     
===============================================
  Files              493      493              
  Lines            54660    54673      +13     
===============================================
+ Hits             32768    32816      +48     
+ Misses           18881    18853      -28     
+ Partials          3011     3004       -7     

Flag	Coverage Δ
unittests	60.02% <43.85%> (+0.07%)	⬆️

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