bump slurm role to v1.4.4: use vars/ for more EL6/EL7 differences
bump slurm role to v1.4.4: use vars/ for more EL6/EL7 differences

 - this means fewer tasks

Testing: fewer debug tasks and install NHC during testing

mantti/fgci-tut,mantti/fgci-tut,CSC-IT-Center-for-Science/fgci-ansible,mantti/fgci-tut