Async tree has the tree store with loaded associated. Whenever a tree node expanded, the loaded get called. However if we fill the tree store with the whole tree data model, when we expad the tree node, the service get called once again. This is not a correct behavior. Since we already add all tree data model into the tree store, it should not call the loader once again when expand the tree node. At least there should be some switch we can turn on or off in terms of loader.