Fix #35807: blender internal motion blur render without antialiasing would
give black speckles (self intersection errors) in raytraced shadows.

Motion blur does some extra offsets for free antialiasing in the motion blur
samples, but did not take them into account everywhere.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57606 954f8c5b-7b00-dc11-b283-0030488c597c