Fixed unit and docker tests

[hallvictoria]

Description

Fixes: flaky stein tests, flaky dispatcher tests, filename docker tests

Fixes #

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PR information

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• If applicable, the PR references the bug/issue that it fixes in the description.
• New Unit tests were added for the changes made and CI is passing.

Quality of Code and Contribution Guidelines

• I have read the contribution guidelines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.19%. Comparing base (7de7724) to head (a6528ce).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1438      +/-   ##
==========================================
- Coverage   85.44%   85.19%   -0.26%     
==========================================
  Files          35       35              
  Lines        1965     1965              
  Branches      370      370              
==========================================
- Hits         1679     1674       -5     
- Misses        213      217       +4     
- Partials       73       74       +1     

Flag	Coverage Δ
unittests	85.13% <ø> (-0.26%)	⬇️

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[gavin-aguiar]

We might not need this. Fix is merged in https://github.com/Azure/azure-functions-python-worker/pull/1433/files#diff-dacb06325e238907a66f886723a814f050200671ac13c92c92e87b35590095ce