ENYO-544: Don't call stabilize() on every setScroll[X|Y]

In the fix for ENYO-483, we introduced a call to stabilize()
every time setScrollX() or setScrollY() was called. This seemed
like a logical place to clamp the scroll position and eliminated
the need for some manual calls to stabilize() elsewhere, but it
turns out that some existing behavior in moon.ScrollStrategy
depends on allowing the position to be temporarily out of bounds.

The Moonstone behavior is complicated, but seems to be reasonable,
so reverting this particular change (affecting ScrollMath,
TouchScrollStrategy and TranslateScrollStrategy). The corresponding
change is also being made in moon.ScrollStrategy.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)