Trying to prevent the grpc setup from being flaky

[antonpirker]

Automatically select a port and not set it by hand also make creating of the channel more stable.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.53%. Comparing base (5147ab9) to head (bde3e15).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4233      +/-   ##
==========================================
+ Coverage   79.52%   79.53%   +0.01%     
==========================================
  Files         142      142              
  Lines       15898    15898              
  Branches     2721     2721              
==========================================
+ Hits        12643    12645       +2     
  Misses       2389     2389              
+ Partials      866      864       -2     

see 4 files with indirect coverage changes

[antonpirker]

I have now run the tests five times in a row without the grpc tests being flaky, so I guess this works. (the last time another flaky test failed, but it was not grpc)