libhb: enable crc checking of audio streams during audio parameter probe

We used to check ac3 crc's when we used a52 dec.  When we switched to libav
we did not enable crc checks.  I suspect this is the root cause of this
problem https://forum.handbrake.fr/viewtopic.php?f=12&t=31032


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6507 b64f7644-9d1e-0410-96f1-a4d463321fa5