policy: don't use EdgeGestureService for navigation bar if were on the keyguard

with this option enabled if you swipe from off the screen to unlock it will not register
the first time requiring a second swipe.

Patch set 2: don't disable as default

Patch set 3: use !isStatusBarKeyguard() thanks to Kiril Mikos

Change-Id: I7b2bf3002bd510df3b65a2d533933ebd81188e70