Fix issue where scrim would be transparent

This is due to BiometricUnlockController#isBiometricUnlock() returning
true after finishing unlocking.

In order to have a more resilient logic, we can also verify if they
device is already unlocked and the keyguard is gone.

Test: manual
Test: atest StatusBarTest
Fixes: 200882274
Change-Id: I4e0aeeec407db1a9dcbcad2960315cb68d7ac3b3