TLTreeTableViewController asynchronously expanding nodes should work if the parent node is collapsed during the operation

[wtmoose]

When asynchronously loading child nodes when the node is expanded, if the parent node is collapsed before the children have finished loading, thus hiding the node that is being populated, the call to setNewVersionOfItem is ignored because it only considers visible nodes. So the next time the node is expanded, the data will need to be loaded again.

Improve this such that the initial load is saved.