dotnet test - fix generating xml for test coverage

[petrsvihlik]

commented out in: https://github.com/petrsvihlik/WopiHost/blob/master/appveyor.yml

https://github.com/OpenCover/opencover/issues/601#issuecomment-289405262

Resources:

• http://foreverframe.net/integrating-codecov-with-net-core-app-appveyor-and-github/
• https://www.appveyor.com/blog/2017/03/17/codecov/
• https://joaorosa.io/2016/10/12/integrate-net-core-appveyor-opencover-and-codecov/

[petrsvihlik]

consider https://www.codefactor.io and codeclimate too

[petrsvihlik]

https://blog.markvincze.com/setting-up-coveralls-for-a-net-core-project/

[petrsvihlik]

https://github.com/OpenCover/opencover/wiki/Usage

[petrsvihlik]

https://dev.to/codingdefined/how-i-added-appveyor-codecov-to-net-core-open-source-project-54m6 https://foreverframe.net/integrating-codecov-with-net-core-app-appveyor-and-github/ https://github.com/codecov/codecov-exe

[petrsvihlik]

consider setting thresholds: https://docs.codecov.io/docs/commit-status

done: codecov, codeclimate, codefactor