Run coverage in parallel mode

[benjaoming]

Summary

Been wondering a bit why coverage isn't showing up properly for kalite.cli so trying out this, even though I think CodeCov already knows that it's receiving separate reports from both CircleCI instances...

[codecov-io]

Codecov Report

Merging #5443 into 0.17.x will decrease coverage by 3.91%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           0.17.x    #5443      +/-   ##
==========================================
- Coverage   51.94%   48.02%   -3.92%     
==========================================
  Files         143      120      -23     
  Lines        7466     6599     -867     
==========================================
- Hits         3878     3169     -709     
+ Misses       3588     3430     -158

Impacted Files	Coverage Δ
kalite/cli.py	28.94% <0%> (-0.1%)	⬇️
kalite/inline/api_urls.py	100% <0%> (ø)	⬆️
kalite/inline/narratives.py	100% <0%> (ø)	⬆️
kalite/updates/urls.py	100% <0%> (ø)	⬆️
kalite/distributed/forms.py	100% <0%> (ø)	⬆️
kalite/contentload/api_urls.py	100% <0%> (ø)	⬆️
kalite/coachreports/api_urls.py	100% <0%> (ø)	⬆️
kalite/control_panel/urls.py	100% <0%> (ø)	⬆️
kalite/distributed/features/steps/generic.py
kalite/coachreports/features/steps/coachreports.py
... and 24 more

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[benjaoming]

Merging #5443 into 0.17.x will decrease coverage by 0.01%.

[benjaoming]

Merging #5443 into 0.17.x will decrease coverage by 3.98%.
The diff coverage is n/a.

[benjaoming]

Wat on earth

Merging #5443 into 0.17.x will decrease coverage by 4.55%.
The diff coverage is n/a.

[benjaoming]

I understand now that the decrease in coverage is because I started ignoring BDD test steps and features, which had pretty high 'coverage' (because they were the test code).

[benjaoming]

I can see coverage of kalite.cli locally but not in the online CodeCov report. Closing this PR and opening a new one in order to figure out if CodeCov isn't doing what it's supposed to.