fix: example server crash on insecure SSL

[alexeldeib]

Fixes the async-h1-server example in case of insecure SSL connection

before:

ace@ace-home-vm:~/code/smol/examples$ cargo run --example async-h1-server
   Compiling smol-examples v0.0.0 (/home/ace/code/smol/examples)
    Finished dev [unoptimized + debuginfo] target(s) in 2.53s
     Running `/home/ace/code/smol/target/debug/examples/async-h1-server`
Listening on http://127.0.0.1:8000
Listening on https://127.0.0.1:8001
Error: error:14094418:SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca:../ssl/record/rec_layer_s3.c:1528:SSL alert number 48

Caused by:
    error:14094418:SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca:../ssl/record/rec_layer_s3.c:1528:SSL alert number 48
ace@ace-home-vm:~/code/smol/examples$ 

after:

ace@ace-home-vm:~/code/smol/examples$ cargo run --example async-h1-server
   Compiling smol-examples v0.0.0 (/home/ace/code/smol/examples)
    Finished dev [unoptimized + debuginfo] target(s) in 2.69s
     Running `/home/ace/code/smol/target/debug/examples/async-h1-server`
Listening on http://127.0.0.1:8000
Listening on https://127.0.0.1:8001
Failed to establish secure TLS connection: Ssl(
    Error {
        code: ErrorCode(
            1,
        ),
        cause: Some(
            Ssl(
                ErrorStack(
                    [
                        Error {
                            code: 336151576,
                            library: "SSL routines",
                            function: "ssl3_read_bytes",
                            reason: "tlsv1 alert unknown ca",
                            file: "../ssl/record/rec_layer_s3.c",
                            line: 1528,
                            data: "SSL alert number 48",
                        },
                    ],
                ),
            ),
        ),
    },
    X509VerifyResult {
        code: 0,
        error: "ok",
    },
)

[alexeldeib]

simple-server has the same problem, but because of how the task gets spawned off it's not immediately clear to me what the best way to handle the error is. Maybe just:

Task::spawn(serve(stream, tls.clone())).expect("failed to serve request").detach();

?

I know it's just an example, so maybe the panics are fine.

[ghost]

Thanks for the PR! I've already got simple-server working so I'll apply these changes to it :)