Do not lock headless system user 0 data

Bug: 161541858
Test: manual with EmbeddedKitchenSinkApp; lock user 0 should return
IllegalArgumentException

Change-Id: Idd707f217c063a1fcb963e2b9c67435dd554a51d

services/core/java/com/android/server/StorageManagerService.java

@@ -3238,6 +3238,12 @@ class StorageManagerService extends IStorageManager.Stub
 
     @Override
     public void lockUserKey(int userId) {
+        //  Do not lock user 0 data for headless system user
+        if (userId == UserHandle.USER_SYSTEM
+                && UserManager.isHeadlessSystemUserMode()) {
+            throw new IllegalArgumentException("Headless system user data cannot be locked..");
+        }
+
         enforcePermission(android.Manifest.permission.STORAGE_INTERNAL);
 
         try {