PMM-13881 fix MongoDB Exporter version detection

[ademidoff]

PMM-13881

Link to the Feature Build: SUBMODULES-3940

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:

• https://github.com/percona/mongodb_exporter/pull/1094

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 44.14%. Comparing base (6be8951) to head (842ae1c).

Additional details and impacted files

@@           Coverage Diff           @@
##               v3    #4050   +/-   ##
=======================================
  Coverage   44.14%   44.14%           
=======================================
  Files         369      369           
  Lines       45326    45326           
=======================================
  Hits        20008    20008           
+ Misses      23633    23631    -2     
- Partials     1685     1687    +2     

Flag	Coverage Δ
admin	17.27% <ø> (+0.04%)	:arrow_up:
agent	52.58% <ø> (-0.02%)	:arrow_down:
managed	44.99% <ø> (ø)
vmproxy	73.45% <ø> (ø)

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