Get the given number of queued jobs uuids. - start - Integer - Position of the first job to retrieve - stop - Integer - Position of the last job to retrieve, _included_ - callback - f(err, jobs)
function nextJobs(start, stop, callback) {
            if (queued_jobs.length === 0) {
                return callback(null, null);
            }

            var slice = queued_jobs.slice(start, stop + 1);

            if (slice.length === 0) {
                return callback(null, null);
            } else {
                return callback(null, slice);
            }
        }