bd: fix long delays caused by updated libbluray

bd_seek and the new m2ts_filter in libbluray have a bad interaction.
So use bd_seek_time instead.


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6221 b64f7644-9d1e-0410-96f1-a4d463321fa5