Fixed Coverity issue 1147771. Write to pointer after free
in req_modifyjob for the asynchonous case.

Fixed Coverity issue 1147770. We were reading a variable after
it had been freed in get_next_retryable_jobid.

Added fixes for Coverity bugs 1147764, 1147765 and 1147766.
rc was possibly used uninitialized in each of these cases.
TRQ-2424