Fix PIN/password lock UI update when locked out.

The ConfirmLockPassword screen (responsible for both PIN and password
locks) should not accept any input during the lock-out period after
consecutive incorrect unlock attempts. However, this is broken if the
activity is resumed from a paused state (e.g. from Recents).

In this CL, we clean up the logic around updating the UI controls, which
fixes the issue above and also hopefully simplifies potential future
work.

Bug: 63277910
Test: make RunSettingsRoboTests
Test: manual, both unified and separate work challenge
Change-Id: I752a5911d4445bf0caeea299ca3eb182e1defc62