sys user split: first pass updating Settings

Update various places in Settings to use "admin" ueser flag
instead of checking user id "0".  This should be no-op in
single user mode since the only admin user would be user 0.
In split system user mode, this will correctly ACL admin
user instead of non-interactive system user.

Bug: 19913735
Change-Id: Ida4d59c5f689ea0dc34b3b3ff0822b087fa0afd6

src/com/android/settings/users/UserDetailsSettings.java

@@ -111,8 +111,8 @@ public class UserDetailsSettings extends SettingsPreferenceFragment
     @Override
     public boolean onPreferenceClick(Preference preference) {
         if (preference == mRemoveUserPref) {
-            if (UserHandle.myUserId() != UserHandle.USER_OWNER) {
-                throw new RuntimeException("Only the owner can remove a user");
+            if (mUserManager.isAdminUser()) {
+                throw new RuntimeException("Only admins can remove a user");
             }
             showDialog(DIALOG_CONFIRM_REMOVE);
             return true;