shutdown: prevent core dumps in final shutdown stage

If the system is finally shutting down it makes no sense to write core
dumps as the last remaining processes are terminated / killed. This is
especially significant in case of a "force reboot" where all processes
are hit concurrently with a SIGTERM and no orderly shutdown of
processes takes place.

src/core/shutdown.c

@@ -323,6 +323,9 @@ int main(int argc, char *argv[]) {
         if (!in_container)
                 sync_with_progress();
 
+        /* Prevent coredumps */
+        disable_core_dumps();
+
         log_info("Sending SIGTERM to remaining processes...");
         broadcast_signal(SIGTERM, true, true);