ENH: remove log calls in ratingscale.draw()

was logging setting units every frame
If this method should be consistent with the format of other set*() methods, it would be

``
def setUnits(self, value, log=True):
    setAttribute(self, 'units', value, log=log)
``

And then called as 
``setUnits(u'norm', log=False)  # no logging``