Exempt the notification panel from animation lockout.

We do a lot of launch-app-then-collapse, and it's a game to
see whether the app's window activity animation starts
before the panel has a chance to finish collapsing.

The winning move here is not to play.

Requires change I2773601d in f/b.
Bug: 8666124

Change-Id: I3e3f1c5a4a505ad7d487c804139445ffd499d8d4