This is the framework change needed to switch from Face Unlock as
a standard unlock mechanism to Face Unlock as a trustlet. This
forces isBiometricWeakInstalled() to return false such that neither
keyguard nor Screen Lock Settings thinks it exists. This means FUL
is no longer a screen lock option.
If Face Unlock was already enabled and someone updates to this build,
the screen lock automatically switches to the backup lock. That
functionality was already built-in so everything would continue to
work if Face Unlock decided to disappear from someone's device.
Change-Id: I407f6e1d75bfe40c7142c2508c2d68867e02d858
a0ee004abf