optimize code for restore exists resources

[cleverhu]

Thank you for contributing to Velero!

Please add a summary of your change

Optimize the previous logic and handle errors uniformly. If the resource exists but cannot be found, the 'get' error will be returned; otherwise, the creation error will be returned.

Does your change fix a particular issue?

Fixes #5288

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• 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.

[cleverhu]

@sseago I think the logic modified now is equivalent to that before. Can you help me see what is wrong with my understanding.

[sseago]

The biggest difference with this version is that in the "object doesn't exist" case, instead of adding restoreErr as a restore error, we add err -- so instead of the error returned by the create call, we're recording the "not found" error returned by the get call.

[cleverhu]

The biggest difference with this version is that in the "object doesn't exist" case, instead of adding restoreErr as a restore error, we add err -- so instead of the error returned by the create call, we're recording the "not found" error returned by the get call.

@sseago I submitted a new version. What do you think of this version? I always feel a little strange about the previous writing.

[cleverhu]

@dsu-igeek @blackpiglet I'm sorry,I clicked the wrong button. I want @shubham-pampattiwar to help me review again instead of cancelling your review request. /PTAL