Fix work badge becoming black in groups

Also make sure the icons disappear in child notifications properly.

Fix: 376689932
Bug: 371174789
Test: post two notifications from the work profile so they get grouped,
check that the workbadge is still blue
Flag: android.app.notifications_redesign_app_icons

Change-Id: I30f878982b07e696caa792273968179e1a1ecd5c