fix MaxJobCount enforcement race condition

Eliminate race condition in enforcement of MaxJobCount limit for job arrays.
The job count limit was checked for a job array before setting the slurmctld
job locks. If new jobs were submitted between the test and the job array
creation such that the job array creation would result in MaxJobCount being
exceeded, then a fatal error would result.
bug 1091
Merge branch 'slurm-14.03'

Conflicts:
	src/slurmctld/job_mgr.c