Add FaceManager.LockoutResetCallback from a bgThread

In case it takes a while to be added. We don't want
to block the main thread.

Fixes: 326147792
Test: Observe face unlock lockout can still be reset after a
successfuly primary authentication
Test: atest DeviceEntryFaceAuthRepositoryTest
Flag: None

Change-Id: Ia68c07cbd6aeb6e27a1f59747d028d34ea0444a7