Prevent 2nd action down motionevent on nav bar press

Since motions events are proxied to launcher on intercept and on touch,
when user touches it used to send both. Prevent the action down proxy
event onTouchEvent will only send one touch event if nothing else
handles it.

Bug: 67957962
Test: manual
Change-Id: Ia2a6bfe6cd963f9383a1468f5ba64dc28005a394