add procmgt systemd ExecStartPre commands to clean up old buffers before starting

systemd/dmt-procmgt@.service

@@ -3,11 +3,22 @@ Description=DMT procmgt service %i
 After=network-online.target
 
 [Service]
+# clear out any old shared memory partitions before starting the
+# process manager.  This would maybe more natuarlly be an
+# ExecStopPost, but those commands are given the exit status of the
+# ExecStart command, which is not what we want here.  NOTE the '-'
+# before the script path that indicates that the exit status of this
+# command is to be ignored.
+ExecStartPre=-~/scripts/shm_all smkill
+# add a little bit of extra time before starting, to ensure that any
+# lingering stuff after a previous stop isn't lying around.  This also
+# would be better done after stop, but we need to find the cleanest
+# way to handle that.
+ExecStartPre=/bin/sleep 5
+# FIXME: check that there's not a way to do these pre-start checks
+# after shutdown.
 ExecStart=/usr/bin/procmgt --file:/home/dmtexec/procmgt/%i --runlist start
-# wait extra time because procmgt doesn't always wait for all it's
-# children before exiting.  We do this as an ExecStopPost so that it
-# happens in all cases, not just on auto-restarts.
-ExecStopPost=/bin/sleep 10
+# FIXME: do we want to auto restart?
 # Restart=always
 # RestartSec=10