Hide UDFPS background on transition Home => AOD

There are two transitions that end up on AoD:
 1. Lock screen => AoD
 2. Home => AoD

We need to track these two transitions separately.
 * When the device transitions from LS => AoD, the icon
has a circle background protection and shows and full
(not dashed) icon.
 * When the device transitions from Home => AoD, the icon
 can immediately start appearing at its AoD location,
 showing the AoD-dashed UDFPS icon, without any bg protection.

Fixes: 229047979
Test: atest UdfpsKeyguardViewControllerTest
Test: enable AoD & enroll UDFPS, press power button from HOME or app
Test: enabled AoD & enroll UDFPS, screen timeout from HOME or app
TesT: enable AoD & enroll UDFPS, pull down shade on HOME then press
power button
Change-Id: I10d54121f9da51bd41a5256f82c520935829f1a7

Change-Id: Ib6d82b484075eab8687ecb4c63babb335d34d163