Always allow System user to change device config in case of Multi-user-multi-display (MUMD)

When visible background user (aka MUMD) is enabled, background users are visible on other displays. In this config, some namespaces (right now game_overlay) are not allowed to be updated by any user other than current user. The CL allows SYSTEM user to change that namespace config.

Flag: EXEMPT bug fix

Bug: 375232833
Bug: 361502556
Bug: 328686115
Test: atest GameManagerStatsTests
Test: atest AndroidCarApiTest:android.car.apitest.DeviceConfigTest
Test: atest --user-type secondary_user_on_secondary_display AndroidCarApiTest:android.car.apitest.DeviceConfigTest
Change-Id: I73cd0fae216ab9aecefc2fdb49a719e919c6437a
diff --git a/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java b/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
index a8af43f5..603a911 100644
--- a/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
+++ b/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
@@ -2479,10 +2479,10 @@
         final long identity = Binder.clearCallingIdentity();
         try {
             int currentUser = ActivityManager.getCurrentUser();
-            if (callingUser == currentUser) {
-                // enforce the deny list only if the caller is not current user. Currently only auto
-                // uses background visible user, and auto doesn't support profiles so profiles of
-                // current users is not checked here.
+            if (callingUser == currentUser || callingUser == UserHandle.USER_SYSTEM) {
+                // enforce the deny list only if the caller is not current user or not a system
+                // user. Currently only auto uses background visible user, and auto doesn't
+                // support profiles so profiles of current users is not checked here.
                 return;
             }
         } finally {