Fix slurmd/slurmstepd daadlock condition

This patch was previously applied to SLURM v2.4 and is being back-ported
due to problems being reported in SLURM v2.3. Original commit is here
https://github.com/SchedMD/slurm/commit/4c0eea7b8c20ccb1cacad51838a1ea8257cc637d