Add property update for radial control operator. It will be necessary
for upcoming overlay refresh commit, but since that commit is becoming
too big, better have this separate to avoid getting this lost in the
noise.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55993 954f8c5b-7b00-dc11-b283-0030488c597c