Fix typo.
USR2 signal will toggle a state where the server will finish current the job,
write next job to the filesystem (if it exists) and then stop the server.
Rename toggle-halt... to just toggle-halt.
When requested make the server halt at the end of a request
instead of near the beginning (but after the job is taken off the
AMQP queue and written to disk). This requires checking in two places,
but is a lot more logical.