Improve behavior of the AJAX.

#5817 
The problem was that when the user delete the author it was removed for the form but not from the node. There for when a user remove the author and added another person again the author that the user removed was back again the form.

One thing that i not yet fixed is: when the user delete all the authors from the last author to the first the form act OK. But when i the user delete all the users from the first author to the last one and then add another author the form will act a little bit strange. I think this is minor problem so we can try to fix this later.