Remove our forcing of analyzeduration and probesize as they seem to

Remove our forcing of analyzeduration and probesize as they seem to
cause weird problems when scanning some files.  The unit test case
added here is a case in point: before this patch one
stream reported an incorrect channel count and sample rate.

It's a bit worrying as these parameters have been in DoM for many years,
but perhaps they have become unnecessary / harmful with changes to FFmpeg.