SystemUI: improve exiting edit mode from qs settings

When the user hits done while in edit mode on the QS Settings page, the
animation can be a little jarring to move to the first page while the
brightness view slides into place. So let's immediately put the
brightness view into its proper position when going out of editing mode
on the settings page.

Ref: OPO-425

Change-Id: I93794a94752978b1055911bbef19ee9f0d77bd3c
Signed-off-by: Roman Birg <roman@cyngn.com>