AOD setting availability depends on other user settings

Bug: 62918778
Test: make
ROBOTEST_FILTER=AmbientDisplayAlwaysOnPreferenceControllerTest
RunSettingsRoboTests -j
Change-Id: Id6f1ad580cf5caace82a1bfa85e85b98f134f9d6

tests/robotests/src/com/android/internal/hardware/AmbientDisplayConfiguration.java

@@ -62,6 +62,10 @@ public class AmbientDisplayConfiguration {
         return true;
     }
 
+    public boolean alwaysOnAvailableForUser(int user) {
+        return true;
+    }
+
     public boolean available() {
         return true;
     }