Update Docker CI entrypoint script

[vitodb]

This PR updates the Docker entrypoint script used by the CI to allow all unit test for to run.
Specifically this PR unset PROMETHEUS_MULTIPROC_DIR env variable.
This var is set in the framework Dockerfile, and this is causing test_check_metrics_env_var_unset test to fail.

[codecov]

Codecov Report

Merging #646 (fafd699) into master (e10fe5a) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #646      +/-   ##
==========================================
+ Coverage   97.51%   97.55%   +0.03%     
==========================================
  Files          49       49              
  Lines        2941     2941              
  Branches      469      469              
==========================================
+ Hits         2868     2869       +1     
  Misses         49       49              
+ Partials       24       23       -1     

Flag	Coverage Δ
python-3.10	97.31% <ø> (ø)
python-3.6	97.09% <ø> (ø)

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Impacted Files	Coverage Δ
.../decisionengine/framework/engine/DecisionEngine.py	93.62% <0.00%> (+0.17%)	⬆️

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