Bug: Cannot make a request without retries

[apohrebniak]

The coap_client::RequestOptions structs has a retries field that specifies a number of request retries. Following a field documentation, one might think that by setting retries: 0, the client would perform a request only once.

However, this tests succeeds:

    #[tokio::test]
    async fn would_fail() {
        let _ = SimpleLogger::init(LevelFilter::Debug, Config::default());

        let mut client = TokioClient::connect("coap://coap.me:5683", &ClientOptions::default())
            .await
            .unwrap();

        let opts = RequestOptions {
            retries: 0,
            timeout: Duration::from_secs(1000),
            ..Default::default()
        };

        let resp = client
            .get("hello", &opts)
            .await;

        assert!(resp.is_err());
        if let Err(Error::Transport(err)) = resp {
            assert_eq!(err.kind(), ErrorKind::TimedOut);
        }

        client.close().await.unwrap();
    }