coverage report file names are somewhat redundant

same for html and xml ; we shoud prefer a shorter form

[coverage_report-coverage_nano.html](https://openqa.opensuse.org/tests/5138848/file/coverage_report-coverage_nano.html)
 [coverage_report-coverage_nano.xml](https://openqa.opensuse.org/tests/5138848/file/coverage_report-coverage_nano.xml)

`coverage_report-$BINARY` might be enough  
