Fix RemainAfterExit services keeping a hold on console

When a service exits succesfully and has RemainAfterExit set, its hold
on the console (in m->n_on_console) wasn't released since the unit state
didn't change.

src/core/unit.c

@@ -1490,6 +1490,9 @@ void unit_notify(Unit *u, UnitActiveState os, UnitActiveState ns, bool reload_su
         if (UNIT_IS_INACTIVE_OR_FAILED(ns))
                 unit_destroy_cgroup(u);
 
+        /* Note that this doesn't apply to RemainAfterExit services exiting
+         * sucessfully, since there's no change of state in that case. Which is
+         * why it is handled in service_set_state() */
         if (UNIT_IS_INACTIVE_OR_FAILED(os) != UNIT_IS_INACTIVE_OR_FAILED(ns)) {
                 ExecContext *ec = unit_get_exec_context(u);
                 if (ec && exec_context_may_touch_console(ec)) {