enhancement(slurmctld): SignalChildrenProcesses

Slurm process tracking is currently not configured to kill child
processes of a job. By default, set SignalChildrenProcesses=yes in
cgroup.conf to enable this functionality.

charms/slurmctld/charmcraft.yaml

@@ -101,6 +101,7 @@ config:
         ConstrainDevices=yes
         ConstrainRAMSpace=yes
         ConstrainSwapSpace=yes
+        SignalChildrenProcesses=yes
       description: |
         User supplied configuration for `cgroup.conf`.