lineage: Allow background broadcast for CAMERA_BUTTON

This enables launch of camera app (snap) when pressing the camera button.

Change-Id: I76fd622031f628b20212e8c7a6239b49fd121a2e

config/permissions/lineage-sysconfig.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2017 The LineageOS Project
+<!-- Copyright (C) 2017-2018 The LineageOS Project
 
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 
     <!-- Broadcast actions that are currently exempted from O+ background
          delivery restrictions. -->
+    <allow-implicit-broadcast action="android.intent.action.CAMERA_BUTTON" />
     <allow-implicit-broadcast action="lineageos.intent.action.INITIALIZE_LINEAGE_HARDWARE" />
     <allow-implicit-broadcast action="lineageos.intent.action.LID_STATE_CHANGED" />