fix: reduce the impact of Redis cluster intermediate states

[xiaozhuang-a]

Description

ensure that clusterSize and statefulset are consistent

Fixes #ISSUE

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist

• Tests have been added/modified and all tests pass.
• Functionality/bugs have been confirmed to be unchanged or fixed.
• I have performed a self-review of my own code.
• Documentation has been updated or added where necessary.

Additional Context

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 44 lines in your changes missing coverage. Please review.

Project coverage is 30.02%. Comparing base (60ef5a2) to head (fc8e3e6).
Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
...ontrollers/rediscluster/rediscluster_controller.go	0.00%	26 Missing and 1 partial ⚠️
pkg/k8sutils/statefulset.go	0.00%	9 Missing ⚠️
pkg/k8sutils/cluster-scaling.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1178      +/-   ##
==========================================
- Coverage   30.20%   30.02%   -0.18%     
==========================================
  Files          55       55              
  Lines        6294     6411     +117     
==========================================
+ Hits         1901     1925      +24     
- Misses       4200     4287      +87     
- Partials      193      199       +6     

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[drivebyer]

lgtm