rpm: call +needs-restart in parallel

Some rpms install a bunch of units… It seems nicer to invoke them all in
parallel. In particular, timeouts in systemctl also run in parallel, so if
there's some communication mishap, we will wait less.

src/rpm/systemd-update-helper.in

@@ -32,8 +32,9 @@ case "$command" in
         [ -d /run/systemd/system ] || exit 0
 
         for unit in "$@"; do
-            systemctl set-property "$unit" Markers=+needs-restart || :
+            systemctl set-property "$unit" Markers=+needs-restart &
         done
+        wait
         ;;
 
     system-reload-restart|system-reload|system-restart)