libceph: move a dout in queue_con_delay()

The queued con->work can start executing (and therefore logging)
before we get to this "con->work has been queued" message, making
the logs confusing.  Move it up, with the meaning of "con->work
is about to be queued".

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>