[chore] avoid flaky test by using port 0

[atoulme]

Description

Use port zero since we just start and stop the server.

Link to tracking issue

Fixes #9772

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.38%. Comparing base (49339e8) to head (305545f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10678   +/-   ##
=======================================
  Coverage   92.38%   92.38%           
=======================================
  Files         403      403           
  Lines       18722    18722           
=======================================
  Hits        17296    17296           
  Misses       1066     1066           
  Partials      360      360           

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[atoulme]

@codeboten please review?

[codeboten]

@atoulme are there other places in the code where this should be changed then?

[atoulme]

@atoulme are there other places in the code where this should be changed then?

yes, there is at least another flaky test that leverages and reuses the same port in between runs, but it specifically tests telemetry and makes calls to the server, which makes things more difficult to move over to this model.
See

opentelemetry-collector/service/service_test.go

Line 308 in ee4eb85

for i := 0; i < 2; i++ {

specifically