Use extension's own copy of dockermod utils

[ycedres]

What does this PR do?

Refactors parts of the code where the utils.dockermod module was being imported from the Salt code instead of from importing it from the extension's code.

What issues does this PR fix or reference?

Fixes: #19

Merge requirements satisfied?

[NOTICE] Bug fixes or new features require tests.

• Docs
• Changelog - https://salt-extensions.github.io/salt-extension-copier/topics/documenting/changelog.html#procedure
• Tests written/updated

Commits signed with GPG?

Yes

Please review Salt's Contributing Guide for best practices.

See GitHub's page on GPG signing for more information about signing commits with GPG.

[codecov]

Codecov Report

❌ Patch coverage is 24.56140% with 43 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.66%. Comparing base (0fe7109) to head (133d0bf).

Files with missing lines	Patch %	Lines
tests/unit/utils/test_dockermod.py	4.44%	43 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #26      +/-   ##
==========================================
+ Coverage   41.90%   42.66%   +0.75%     
==========================================
  Files          26       25       -1     
  Lines        6629     6495     -134     
  Branches     1146     1120      -26     
==========================================
- Hits         2778     2771       -7     
+ Misses       3601     3469     -132     
- Partials      250      255       +5     

Flag	Coverage Δ
Linux	42.64% <24.56%> (+0.75%)	⬆️
project	38.46% <100.00%> (+0.70%)	⬆️
py310	42.60% <24.56%> (+0.75%)	⬆️
py311	42.60% <24.56%> (+0.75%)	⬆️
py314	42.60% <24.56%> (+0.75%)	⬆️
salt_3006_27	42.60% <24.56%> (+0.75%)	⬆️
salt_3008_2	42.60% <24.56%> (+0.75%)	⬆️
tests	50.86% <4.44%> (+1.31%)	⬆️

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