Attempt to fix broken CI tests

[relu91]

Hi, while working on #2811 a stumble upon a random timeout in the test. As described in #2837 I think the problem is when the virtual-adapter plug-in is installed. This PR fixes #2837 by blocking further adapter additions when the plug-in already got an unload request. Furthermore, it now fails gracefully when unload is called more than once.

Finally, I also "improved" the log tests. Basically, in my system, it failed when you already executed the tests (like one day before), because it had a wrong log file count. Now it clears the log folder to have a clean state. Let's hope that now we have a green light 🤞🏻

[codecov-commenter]

Codecov Report

Merging #2841 (cbecf9c) into master (772e98b) will decrease coverage by 1.27%.
The diff coverage is 34.74%.

❗ Current head cbecf9c differs from pull request most recent head 6d37915. Consider uploading reports for the commit 6d37915 to get more accurate results

@@            Coverage Diff             @@
##           master    #2841      +/-   ##
==========================================
- Coverage   66.52%   65.25%   -1.28%     
==========================================
  Files         121      124       +3     
  Lines        7615     7952     +337     
  Branches     1289     1316      +27     
==========================================
+ Hits         5066     5189     +123     
- Misses       2506     2721     +215     
+ Partials       43       42       -1     

Impacted Files	Coverage Δ
src/plugin/adapter-proxy.ts	77.63% <0.00%> (ø)
src/models/group.ts	14.70% <14.70%> (ø)
src/db.ts	68.96% <22.22%> (-8.74%)	⬇️
src/models/groups.ts	26.92% <26.92%> (ø)
src/controllers/groups_controller.ts	27.73% <27.73%> (ø)
src/models/things.ts	76.68% <52.63%> (-5.27%)	⬇️
src/models/thing.ts	69.08% <70.00%> (+0.30%)	⬆️
src/controllers/things_controller.ts	80.31% <83.33%> (-0.08%)	⬇️
src/addon-manager.ts	60.13% <100.00%> (ø)
src/constants.ts	100.00% <100.00%> (ø)
... and 13 more

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