[release-1.13] Refactored the functions cleanUpSPAs and resetObsoleteSPAs

[knative-prow-robot]

This is an automated cherry-pick of #186

[houshengbo]

/lgtm
/approve

[knative-prow]

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 38 lines in your changes are missing coverage. Please review.

Project coverage is 48.12%. Comparing base (ddf75b0) to head (0d9ad86).
Report is 8 commits behind head on release-1.13.

Files	Patch %	Lines
...onciler/rolloutorchestrator/rolloutorchestrator.go	0.00%	38 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.13     #188      +/-   ##
================================================
- Coverage         49.42%   48.12%   -1.31%     
================================================
  Files                23       25       +2     
  Lines              2280     1943     -337     
================================================
- Hits               1127      935     -192     
+ Misses             1109      961     -148     
- Partials             44       47       +3     

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