[cherry-pick]Call WaitGroup.Done() once only when PVB changes to final status the first time to avoid panic

[ywk253100]

Call WaitGroup.Done() once only when PVB changes to final status the first time to avoid panic

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Fixes #(issue)

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[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 59.57%. Comparing base (c2695c3) to head (5ba4bd1).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/podvolume/backupper.go	75.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8941   +/-   ##
=======================================
  Coverage   59.56%   59.57%           
=======================================
  Files         370      370           
  Lines       40267    40278   +11     
=======================================
+ Hits        23987    23995    +8     
- Misses      14778    14780    +2     
- Partials     1502     1503    +1     

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