A side effect of the previous commit's refactoring is that we mark the
pipeline as failed if a (packet loss/bitrate) threshold is violated.
Previously, the HTML would contain a "Perf not met" hint, but be marked
as successful.

This commit introduces more realistic thresholds for various pipeline
runs. The values are arbitary, following the performances in pipelines
that were marked as successful, but actually had performance problems.
They allow, though, a pipeline to pass following the normal performance
we saw the last weeks.