Re-redo not-yet-used connection handling

Re-redo not-yet-used connection handling

Previously we were taking special care to avoid closing connections
that hadn't been used yet, but this is not actually necessary;
run_queue() doesn't prune idle connections until after running through
the entire queue once, so if the new connection is still idle at that
point, it means we no longer have a message to send on it (probably
because the message already got sent on another connection), and so it
is legitimate to close it if needed.

http://bugzilla.gnome.org/show_bug.cgi?id=592084