[core] fix raising E_CORE_PROC_AUTO_SCALE

The event is raised by the attendent process, which is not properly init for all event backends.
So better dispatch the event to the regular workers to be raised.

pt_scaling.c

@@ -247,7 +247,7 @@ static void _pt_raise_event(struct process_group *pg, int p_id, int load,
 		goto error;
 	}
 
-	if (evi_raise_event(EVI_PROC_AUTO_SCALE_ID, list)) {
+	if (evi_dispatch_event(EVI_PROC_AUTO_SCALE_ID, list)) {
 		LM_ERR("unable to send auto scaling event\n");
 	}
 	return;