Release retained STUN port history during final core destruction

src/utun_instance.c

@@ -408,6 +408,7 @@ void utun_instance_destroy(struct UTUN_INSTANCE *instance) {
     
     instance->running = 0;
     stun_nat_destroy(instance);
+    stun_nat_forget_ports(instance);
     etcp_padding_stop(&instance->padding);
     DEBUG_INFO(DEBUG_CATEGORY_SYS, "[DESTROY] A done — diagnose complete");