Enforce policy for camera gesture in keyguard

If the admin has disabled the camera for secure
keyguards, in addition to removing the bottom-right hand
corner camera button do not allow the camera to be opened
via the camera gesture either.

Bug: 63334090
Test: Manually tested launching the camera on secure and non-secure keyguard and non-keyguard, both via camera icon and gesture
Change-Id: I104688eaad719528376e2851f837d5956a6a1169