[test] Fixed tests that were weirdly failing

[ethouris]

Fixed the use of the server pollid in test_reuseaddr.cpp that was a "test global variable" with weird consistency rules.

[codecov]

Codecov Report

Attention: Patch coverage is 91.66667% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 64.82%. Comparing base (2c3f6f9) to head (7e85f0e).
Report is 1 commits behind head on master.

Files	Patch %	Lines
test/test_main.cpp	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2908      +/-   ##
==========================================
+ Coverage   64.76%   64.82%   +0.05%     
==========================================
  Files         101      101              
  Lines       17524    17526       +2     
==========================================
+ Hits        11350    11361      +11     
+ Misses       6174     6165       -9     

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