Suspend auto-hiding taskbar when folder is open

* Notify SystemUi to suspend autoHide behavior
until launcher notifies otherwise
* There's no exclusive lock for AutoHideController
behavior, so down the road another component can
choose to resume auto-hide behavior even if launcher
has requested otherwise (and vice versa),
something to keep in mind.

Fixes: 193938507
Test: Opened folder while in immersive video,
taskbar stayed open.

Change-Id: I12f4055911822893551683466cfd532c8108a3a0