Invalid CDKEY reproduction steps

[Steven Hartland]

Looks like we have hit on repoduction steps for the invalid
CDKEY message.
1. Join a server you have access to.
2. Kill the server
3. Try and rejoin the server after restarting or join another
server.

At a guess its either an internal client flag not being reset
or a client sessionid / auth server thing designed to detect
the use of the same cdkey twice.

    Steve / K