Keaguard: enable translucent keyguard by default

currently it is possible to enable it per device over an overlay and it is disabled
by default. Enable it by default but respect general transluscent disable from
device tree. Manta eg disables this feature due of graphical glichtes.

Change-Id: I3579d47ee3bee05719ef357ffcf19c0137b2302f
Power Menu config (1/2)