Prevent the bouncer from showing over dreams when swiping down the

shade.

Currently, since the bouncer and notification shade utilize the same
panel, we see the bouncer appear when swiping down the shade. With this
fix, we only allow the bouncer to expand if the shade is not expanded.

Bug: 226419441
Bug: 224996347
Test: locally on device
Change-Id: I6f702cc1d262bb3a0397fadf7f14b8f3c683900d