Handle duplicate DOWN event

After unlocking the device, an immediate swipe down to reveal the
shade (a very common user journey) can sometimes just directly to the
QS shade variant, instead of showing the expected QQS shade with
notifications. I have been unable to find root cause at this point,
however, I am aware that multiple ACTION_DOWN events are issued in
this case with the same downTime.

To fix, detect this very specific scenario and ignore the touch.

Fixes: 193350347
Test: manual, follow steps in bug (swipe down after unlock)
Change-Id: I84ba92fb0cf981b227afdff15cbe41c09ea56f5d