Increase video transcode max time from 8 to 16 hours
Full-length films at HD sometimes take long enough they were
still hitting the increased time limit (compensating for the
threading in ffmpeg and how ulimit handles time). This meant
we were transcoding most of the file, then throwing away the
result after the timeout struck.
Bump up from 8 hour to 16-hour base limit, which should
somewhat increase CPU usage on scalers in exchange for actually
producing results on those long files.
NB: in future it would be great to find a way to reduce
time spent on a single scaler for a high res lnog file.
This will be complicated though, we're stuck with serialized
behavior for now.