Prevent flings after motion gestures on fully expanded keyguard

Any up-down gesture on keyguard would trigger a fling that visibly
jumped the keyguard up due to the different height calculation for
shade vs keyguard. If the gesture was quick enough, we were stuck
with this incorrect expansion fraction until the next touch.
This change simply blocks flings on keyguard off
guestures that end at full expansion.

Test: manual
Bug: 259023628
Change-Id: Id67c0e38cc28a13fd19d23bdd0b6bff31cf1fe30