Don't load app restriction from saved files in test

As it interfers with testing.

Bug: 203105544
Test: atest FrameworksMockingServicesTests:BackgroundRestrictionTest
Change-Id: I6004f924c6e76fce1a9a20d2c26ddb9f4b960988

services/core/java/com/android/server/am/AppRestrictionController.java

@@ -1413,11 +1413,13 @@ public final class AppRestrictionController {
             refreshAppRestrictionLevelForUser(userId, REASON_MAIN_FORCED_BY_USER,
                     REASON_SUB_FORCED_USER_FLAG_INTERACTION);
         }
-        // Load the previously saved levels and update the current levels if needed.
-        mRestrictionSettings.scheduleLoadFromXml();
-        // Also save the current levels right away.
-        for (int userId : allUsers) {
-            mRestrictionSettings.schedulePersistToXml(userId);
+        if (!mInjector.isTest()) {
+            // Load the previously saved levels and update the current levels if needed.
+            mRestrictionSettings.scheduleLoadFromXml();
+            // Also save the current levels right away.
+            for (int userId : allUsers) {
+                mRestrictionSettings.schedulePersistToXml(userId);
+            }
         }
     }
 
@@ -2822,6 +2824,10 @@ public final class AppRestrictionController {
         @CurrentTimeMillisLong long currentTimeMillis() {
             return System.currentTimeMillis();
         }
+
+        boolean isTest() {
+            return false;
+        }
     }
 
     private void registerForSystemBroadcasts() {

services/tests/mockingservicestests/src/com/android/server/am/BackgroundRestrictionTest.java

@@ -3056,6 +3056,11 @@ public final class BackgroundRestrictionTest {
         long currentTimeMillis() {
             return mCurrentTimeMillis;
         }
+
+        @Override
+        boolean isTest() {
+            return true;
+        }
     }
 
     private class TestBaseTrackerInjector<T extends BaseAppStatePolicy>