etc/rc1: do not cancel jobs under system instance

Problem: By default in etc/rc1, a script is setup to cancel all
jobs when the flux broker is brought down on rank 0.  This should
not be done when running the system instance.

Solution: Check if we are running as the system instance by checking
the configuration of systemd.enable via `flux config get`.  If we
are, do not enable job cancelation.

Author: chu11

etc/rc1

@@ -89,10 +89,14 @@ if test $RANK -eq 0 -a "${FLUX_SCHED_MODULE}" != "none" \
     flux module load ${FLUX_SCHED_MODULE:-sched-simple}
 fi
 
-if test $RANK -eq 0 -a -z "${FLUX_DISABLE_JOB_CLEANUP}"; then
+if test $RANK -eq 0; then
+    method=$(flux config get --default=notset exec.method)
+    if test "${method}" != "systemd" \
+            -a -z "${FLUX_DISABLE_JOB_CLEANUP}"; then
 	flux admin cleanup-push <<-EOT
 	flux queue stop --quiet
 	flux job cancelall --user=all --quiet -f --states RUN
 	flux queue idle --quiet
 	EOT
+    fi
 fi