providers:checkbox: piglit_test should call piglit in verbose mode

This is required because piglit output changed and now our parser's expectations are only met by verbose mode. Also, fixed the logic a bit so if our parser didn't parse any results, a loud warning and an error code will be generated, instead of a misleading successful exit code and cryptic "0 tests passed" message. 

0 files changed, 0 insertions, 0 deletions