sql std auth - new users in admin role config should get added

if metastore is started with hive.users.in.admin.role=user1, then user1 is added admin role to metastore.
If the value is changed to hive.users.in.admin.role=user2, then user2 should get added to the role in metastore. Right now, if the admin role exists, new users don't get added.
A work-around is - user1 adding user2 to the admin role using grant role statement.