PMM-12448 Fix bug in backup preconditions check function

[artemgavrilov]

PMM-12448

Link to the Feature Build: SUBMODULES-3371

If this PR adds or removes or alters one or more API endpoints, please review and add or update the relevant API documents as well:

• API Docs updated

If this PR is related to some other PRs in this or other repositories, please provide links to those PRs:

• Links to related pull requests (optional).

[codecov]

Codecov Report

Merging #2437 (abb0e1c) into main (df3b1aa) will decrease coverage by 0.13%.
The diff coverage is 100.00%.

❗ Current head abb0e1c differs from pull request most recent head 84481be. Consider uploading reports for the commit 84481be to get more accurate results

@@            Coverage Diff             @@
##             main    #2437      +/-   ##
==========================================
- Coverage   42.83%   42.71%   -0.13%     
==========================================
  Files         384      384              
  Lines       48233    48196      -37     
==========================================
- Hits        20663    20585      -78     
- Misses      25626    25674      +48     
+ Partials     1944     1937       -7     

Flag	Coverage Δ
managed	43.74% <100.00%> (-0.18%)	⬇️

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Files Changed	Coverage Δ
managed/services/preconditions.go	76.63% <100.00%> (+0.44%)	⬆️

... and 5 files with indirect coverage changes

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