Minor update to the Terenas Lurker raiding info post

[Treesh]

Basically a clarification of how the attendance queue works when you are waitlisted, but end up backfilling for a raid anyway. Those who haven't read the sticky yet (either the edited version or the first version), go read it now.:P

A little bump here since it's been updated again, mostly dealing with signups and attendance. Familiarize yourselves with the slight changes because they are now in effect. :)