More on #7296510 Transition from lock screen to dreaming is really bad

The final iteration of that change was a little too aggresive in
deciding when it turns off the dream's enter animation, so it was
doing this always instead of just when it needed to (when it is
being displayed to hide the lock screen).

This change fixes a dumb typo that was causing the dream to always
turn off its own animation (duh!) and tweaks the logic for deciding
when the dream should be able to cause the lock screen to hide to
better ensure that it is shown before the lock screen gets hidden.

Change-Id: Ie73a5be9ee597713644fb2a0202f36c32b4f1fca