Calling HttpServer's stop method in binding-http returns nothing

The following problem occurred. I apologize for the inconvenience and would appreciate your confirmation.
I would appreciate it if you could tell me if I am calling it the wrong way, etc.

# Problem

Nothing is returned when I call the stop method of HttpServer of Binding-http.
This problem may occur if the property is being observed from the client.

# environment

* Mac(Apple siicon)
* OS: Sonoma 14.1
* nodejs: v18 or v20
* node-wot: 0.8.12

# Steps to reproduce

get the following code

https://github.com/hidetak/test-node-wot/tree/main/no-stop-httpserver

1. $ npm install
1. $ npm run start:server
1. open new terminal
1. $ npm run start:client
1. After 10 seconds have elapsed since the server was started, the termination process begins (The following text will appear in the terminal where the server is run)
```
[debug] endServient called.
[debug] server destroyed.
```
If 3 and 4 are not performed, the following is displayed and appears to be correctly terminated.
```
[debug] endServient called.
[debug] server destroyed.
[debug] server stopped.
[debug] servient shutdown.
```

Trước tiên, hãy chạy bản tái hiện no-stop-httpserver từ repository được liên kết bằng npm install, npm run start:server và npm run start:client. Theo dõi đường dẫn dừng của HttpServer sau khi client quan sát thuộc tính; hoàn tất có nghĩa là log shutdown đạt tới “server stopped” và “servient shutdown” trong kịch bản đó.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.