Useful if you want to keep AdminCcs in the loop about a ticket until an
Owner is assigned and then want them to stop getting email.  Nothing
uses it by default.

The smallest code override I came up with was to lie in Argument for
Notify, so we just return Owner or AdminCc for "who to notify" depending
on the Owner of the ticket.  Doesn't handle the case where you set an
Owner during a reply because of update ordering on Display.html.