Don't reposition the clock when pulling down the notification bar

positionClockAndNotifications() is causing the digital clock to
abruptly fade and shrink when pulling down the notification bar,
while it should slowly fade away and only while swiping up to
unlock the screen.

Change-Id: I455798c1dfc880353334dbe9d1b8ac0c6b5bc87c
(cherry picked from commit fc18fac6)