SystemUI: Unbreak the planet

 * Not sure who to blame, but it's probably themes... :)

Change-Id: I0c534354a699f756d809aff10843ebea21f3f369
SystemUI: Fix crash during notification/theme change

Fixes crashing that could occur when a notification is created
during a theme change. Entries were attempting to be added
to views which did not have a layout pass yet, causing it to fail.

When a theme change occurs, the fix is to halt the ticker and command queue
until a layout occurs.

BUGDUMP-151925

Change-Id: Ic19d26178df673a1d52981a8617415e6fbcb219d