Put dismiss end target at navigation bar

This makes the animation when exiting docked mode a bit nicer
when you fling the divider towards to the navigation bar. However,
since the divider ends at the navigation bar, we need to immediately
dismiss it instead of fading out when the divider is fully occluded
by the navigation bar.

Change-Id: Ic5432fd118cb71be36485667b2c537caf5065ce5