Enforce policy for camera gesture in keyguard

Test:
1. Set lock screen, set keyguard policy. Lock the device.
   Observe that double tap is not showing camera

2. Set lock screen, unset the keyguard policy. Lock the device.
   Observe that double tap is showing camera

3. Unset lock screen (swipe), set the keyguard policy. Lock the device.
   Observe that double tap is showing camera.

4. Unset lock screen (swipe), unset the keyguard policy. Lock the device.
   Observe that double tap is showing camera.

Bug: 63787722
Merged-In: I104688eaad719528376e2851f837d5956a6a1169

Change-Id: I42e6d9015682998176fe41971356bde22e1b37b2