Fix disabled aiokafka unit tests

[wbarnha]

It's going to be hard to investigate what's going on with https://github.com/faust-streaming/faust/issues/175 unless we get better testing in place.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.08%. Comparing base (3d737c7) to head (32e7a51).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #610      +/-   ##
==========================================
+ Coverage   93.69%   94.08%   +0.38%     
==========================================
  Files         102      102              
  Lines       11117    11117              
  Branches     1550     1550              
==========================================
+ Hits        10416    10459      +43     
+ Misses        609      558      -51     
- Partials       92      100       +8     

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