It turns out that the approach of having the HNP do the
fork/exec of MPI ranks on the head node in a SLURM environment
introduces problems when users/sysadmins want to use the SLURM
scancl tool or sbatch --signal option to signal a job.
This commit disables use of the HNP fork/exec procedure when
a job is launched into a SLURM controlled allocation.
update NEWS with a blurb about new ras framework mca parameter.
related to #3998
Signed-off-by: Howard Pritchard <hppritcha@gmail.com>
d08be74573