Avoid wrapping failed PVB status with empty message.

[mrnold]

Please add a summary of your change

This change removes a leading ':' character in the status message of a failed PVB, and changes "get" to "found". For example, from:
: get a podvolumebackup with status "InProgress" during the server starting, mark it as "Failed"
to:
found a podvolumebackup with status "InProgress" during the server starting, mark it as "Failed"

Does your change fix a particular issue?

Fixes #7857

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.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.

Project coverage is 58.82%. Comparing base (55e0278) to head (f8e697d).
Report is 7 commits behind head on main.

Files	Patch %	Lines
pkg/controller/pod_volume_backup_controller.go	0.00%	4 Missing ⚠️
pkg/cmd/cli/nodeagent/server.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8028      +/-   ##
==========================================
- Coverage   58.82%   58.82%   -0.01%     
==========================================
  Files         346      346              
  Lines       28886    28889       +3     
==========================================
  Hits        16993    16993              
- Misses      10464    10467       +3     
  Partials     1429     1429              

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