Fix logic for checking if the queue table exists

This got broken back in 2012 when I rewrote the logic to be cached and got the boolean backwards. See: https://github.com/silverorange/site/commit/7a4b8d4e87590aa5b32045cb2ef13a40efa14772#diff-58c8df2f621fb52cd187768ed7601881R287

I'm not sure how we never noticed this was broken.