screenShield: Tie `LockedHint` to locked state
Currently the hint reflects the active
state, which effectively
corresponds to the screen blank. That's a bit surprising considering
the name, plus the active
state is already exposed by the ScreenSaver
D-Bus interface for anyone interested.
It seems reasonable that the LockedHint
property reflects the lock
state, so change the handling to do exactly that.
Fixes #351 (closed)