Changed job_id to 32 bits per DPCS requirement. Jobs without job_id

specified at submit time start with a value of 1<<16 and DPCS uses
values 1 to 0xffffffff. This preclude effective use of a max job_id
in search function, which was able to quickly indicate that a job_id
requested by DPCS was not already in use. I added a job_id hash table
to restore quick job find operations.