Modify CSI VolumeSnapshot metric related code.

[blackpiglet]

Signed-off-by: Xun Jiang jxun@vmware.com

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Does your change fix a particular issue?

Fixes #2499

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[codecov-commenter]

Codecov Report

Merging #4854 (22dd0b2) into main (3ec96e2) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #4854      +/-   ##
==========================================
- Coverage   41.37%   41.37%   -0.01%     
==========================================
  Files         204      204              
  Lines       18061    18062       +1     
==========================================
  Hits         7473     7473              
- Misses      10041    10042       +1     
  Partials      547      547              

Impacted Files	Coverage Δ
pkg/controller/backup_controller.go	57.26% <0.00%> (-0.11%)	⬇️

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