Block access to accounts for limited users.

Make sure that apps that have access to restricted accounts can see them.
If they don't have access, they shouldn't be able to add a new account either.
Show an error message in the account picker if the user/app is not authorized.

Change-Id: I117c0b14d7d06c5ac4e66506df156b174567f5f3
diff --git a/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java b/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
index 45319a8..659651b 100644
--- a/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
+++ b/packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java
@@ -322,7 +322,7 @@
     @Override
     public boolean onCreate() {
         mBackupManager = new BackupManager(getContext());
-        mUserManager = (UserManager) getContext().getSystemService(Context.USER_SERVICE);
+        mUserManager = UserManager.get(getContext());
 
         setAppOps(AppOpsManager.OP_NONE, AppOpsManager.OP_WRITE_SETTINGS);
         establishDbTracking(UserHandle.USER_OWNER);