Fix get_next_job_id to return fed job id

get_next_job_id() was returning a local id and then the fed_mgr was
turning that into a fed job id. This was a problem because
get_next_job_id() couldn't check to see if an existing job already had
the fed job id. It was only checking for the local job id. This was
exposed in tests that did a reconfigure and the reconfigure loaded in a
old job_id_sequence so that the next job got an id that was already
being used.