Improve CI workflow for Droplet test

[olethanh]

• Only calculate the IP once.
• Do not include the configuration inside the Debian package but modify it directly inside the droplet.

Self proofreading checklist

• The new code clear, easy to read and well commented.
• New code does not duplicate the functions of builtin or popular libraries.
• [N/A] An LLM was used to review the new code and look for simplifications.
• [N/A] New classes and functions contain docstrings explaining what they provide.
• [of course] All new code is covered by relevant tests.
• Documentation has been updated regarding these changes.

[hoh]

Tests on droplets were cancelled, restarted them 😉

[hoh]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.19%. Comparing base (fefb30d) to head (01de28f).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #691   +/-   ##
=======================================
  Coverage   62.19%   62.19%           
=======================================
  Files          69       69           
  Lines        6074     6074           
  Branches      641      641           
=======================================
  Hits         3778     3778           
  Misses       2144     2144           
  Partials      152      152           

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