Block settings when DISALLOW_CONFIG_DATE_TIME.

Test: m -j RunSettingsRoboTests
runtest -x packages/apps/Settings/tests/unit/src/com/android/settings/core/UserRestrictionTest.java

Fix: 67497909

After turn on the user restriction in TestDPC:
https://hsv.googleplex.com/5414119658225664
The date time settings page become:
https://hsv.googleplex.com/5199302573948928


Change-Id: I42590c4a505ec1b6ffa86eb460b90fa6ec8ba783

src/com/android/settings/datetime/AutoTimePreferenceController.java

@@ -46,8 +46,10 @@ public class AutoTimePreferenceController extends AbstractPreferenceController
         if (!(preference instanceof RestrictedSwitchPreference)) {
             return;
         }
-        ((RestrictedSwitchPreference) preference).setDisabledByAdmin(
-                getEnforcedAdminProperty());
+        if (!((RestrictedSwitchPreference) preference).isDisabledByAdmin()) {
+            ((RestrictedSwitchPreference) preference).setDisabledByAdmin(
+                    getEnforcedAdminProperty());
+        }
         ((RestrictedSwitchPreference) preference).setChecked(isEnabled());
     }