Fix quicktime video export not properly supporting animation of audio properties like volume.

Patch #35184 by James Yonan, see the report for a detailed explanation of why this failed.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56494 954f8c5b-7b00-dc11-b283-0030488c597c