run slurmctld as user

Notice: also trying to run slurmd on execute nodes as user makes no
sense because it breaks sbatch. Furthermore there is another necessary
to run mpi jobs (just tried MpiDefault=none). I don't consider running
slurmd as root a good idea, but there seems to be no other choice at the
moment.

roles/slurm/files/slurmd.Dockerfile

@@ -14,6 +14,12 @@ RUN chown root:root /usr/local/sbin/entrypoint.sh && \
 
 ENTRYPOINT [ "/usr/local/sbin/entrypoint.sh" ]
 
+ARG slurmuser=slurm
+ENV slurmuser=${slurmuser}
+
+RUN useradd -d /var/lib/slurm -m --no-log-init --system $slurmuser &&\
+	slurm-setuser -u $slurmuser -g $slurmuser -y
+
 RUN yum install -y slurm-slurmd && \
 	yum clean all && rm -rf /var/cache/yum