Partially revert "Wake up to lock screen when bouncer is visible"

Commit 3cfd6889 causes the screen to
randomly turn back on right after being turned off when a biometric
unlock method is enabled. When this occurs, the following message is
left in logcat:

I PowerManagerService: Waking up from Dozing (uid=10188, reason=WAKE_REASON_GESTURE, details=com.android.systemui:BOUNCER_VISIBLE)...

This occurs even though no gesture has taken place. This can be
especially annoying and even a potential security hazard when face
unlock is used, as the screen turning back on engages the face unlock
process and can unlock the device if the user's face is still visible
to the device.

Change-Id: I3550d9531cfc97be50747c6460c9df237d23b5fb