drawobject: Fix sphere bounds drawing

Would draw ellipsoid instead, which is not so useful and wrong when 
used for rigid body collision shape visualization.

svn merge -r59887:59888 ^/branches/soc-2013-rigid_body_sim


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60917 954f8c5b-7b00-dc11-b283-0030488c597c