Fix issue with a 2.5 slurmstepd locking up when talking to a 2.6 slurmd.
Merge remote-tracking branch 'origin/slurm-2.6'

Conflicts:
	src/common/stepd_api.c
Minor change in error message for better clarity
Sched/backfill - Change default max_job_bf parameter from 50 to 100.

This makes it consistent with the value of default_queue_depth.
The backfill scheduler should be able to easily handle this value
(or much higher for pretty much any configuration).
Fix issue with last patch dealing with deadlock from 2.5 slurmstepd
-> 2.6 slurmd
Merge remote-tracking branch 'origin/slurm-2.6'
Minor spelling corrections
Merge remote-tracking branch 'origin/slurm-2.6'
Sanity check
Merge remote-tracking branch 'origin/slurm-2.6'