PMM-7: extract test env workaround

[idoqo]

PMM-7
CI currently fails because the health checks for pmm-server container is failing. This applies a workaround copied from #2777 as a temporary workaround.

Link to the Feature Build: SUBMODULES-0

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

All modified and coverable lines are covered by tests ✅

Comparison is base (3bb7ec4) 43.46% compared to head (263f632) 43.45%.

Additional details and impacted files

@@            Coverage Diff             @@
##               v3    #2809      +/-   ##
==========================================
- Coverage   43.46%   43.45%   -0.01%     
==========================================
  Files         361      361              
  Lines       42335    42335              
==========================================
- Hits        18399    18397       -2     
- Misses      22369    22373       +4     
+ Partials     1567     1565       -2     

Flag	Coverage Δ
admin	11.54% <ø> (-0.05%)	⬇️
agent	53.37% <ø> (ø)
vmproxy	68.57% <ø> (ø)

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