cleanup restic helper folder when done

[big-appled]

Thank you for contributing to Velero!

Please add a summary of your change

There will be a folder named .velero left in user volume when restore data with restic. We need to remove it when the restic-helper init container done.

Does your change fix a particular issue?

no
Fixes #(issue)

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[ywk253100]

@big-appled Could you explain why we need this change?

[big-appled]

@big-appled Could you explain why we need this change?

@ywk253100 The folder .velero is left in user volume after restore with restic, which will cause errors for some applications. For example, Kafka, which will treat this folder as an index folder and throw error.
So I think we need clean it up after done.

[codecov-commenter]

Codecov Report

Merging #4872 (e09c31e) into main (001229a) will decrease coverage by 0.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #4872      +/-   ##
==========================================
- Coverage   41.25%   41.08%   -0.17%     
==========================================
  Files         204      204              
  Lines       18041    18094      +53     
==========================================
- Hits         7442     7434       -8     
- Misses      10047    10109      +62     
+ Partials      552      551       -1     

Impacted Files	Coverage Δ
pkg/controller/backup_controller.go	48.07% <0.00%> (-9.93%)	⬇️
pkg/controller/backup_sync_controller.go	58.82% <0.00%> (-2.72%)	⬇️
pkg/controller/pod_volume_backup_controller.go	44.14% <0.00%> (-0.78%)	⬇️
pkg/util/kube/utils.go	74.28% <0.00%> (-0.72%)	⬇️
pkg/restore/restore.go	66.02% <0.00%> (-0.68%)	⬇️
pkg/cmd/server/server.go	6.89% <0.00%> (-0.04%)	⬇️
pkg/controller/pod_volume_restore_controller.go	24.78% <0.00%> (+1.43%)	⬆️
pkg/cmd/cli/restic/server.go	18.06% <0.00%> (+3.01%)	⬆️

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