Fix save button activation on case list page of Advanced/CommTrack modules 

[Ticket](http://manage.dimagi.com/default.asp?146935)

Fixes a bug where the save button of the case list page for advanced modules would not activate if sort properties where modified.
This was the problematic line. Advanced modules have two, `DetailScreenConfig` objects, each with a "list" `Screen` object, that is, a Case List and Product List. When the Product List was initialized, the `window.sortRowSaveButton` is set to be the Product List save button. Therefore, alterations to the Case List save properties were activating the Product List save button, and not the Case List save button as expected.