Fix bug and add logging in FalsingManager

Fixes bug that lead FalsingManager to be incorrect
about the screen on state.

Makes it a fatal error to query whether a touch is
falsing outside of an active session.

Prevents touch collection and logging on the locked
shade which needs no anti-falsing.

Bug: 27227578
Change-Id: I8e330ad28636156a952e61b8fe6a3d201f82e624