director: Keep users unsorted during handshake and sort them at the end

director: Keep users unsorted during handshake and sort them at the end

This is simpler and sometimes more efficient than the current way of
immediately inserting the users to the correct place in the linked list.
This is especially useful if handshaking is mixed with regular USER updates,
because each switch between them required walking the linked list backwards
to find the proper insert position.

It's not a big problem if the users list is temporarily unordered. It mainly
means that some of the users won't be expired as early as they should have.