gpservice crashes if can't bind to port

[timp87]

Describe the bug
gpservice crashes if can't bind to port. For example, you can try starting it under non-root user.

https://github.com/yuezk/GlobalProtect-openconnect/blob/v2.2.1/apps/gpservice/src/ws_server.rs#L124

Expected behavior
Output a perror and exit.

Logs

[2024-05-10T03:07:09Z INFO  gpservice::cli] gpservice started: 2.2.1 (2024-05-08)
thread 'tokio-runtime-worker' panicked at apps/gpservice/src/ws_server.rs:124:58:
called `Result::unwrap()` on an `Err` value: Permission denied (os error 13)
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Abort trap (core dumped)

Environment:

• FreeBSD 13.3-RELEASE-p1 amd64
• GlobalProtect-openconnect-2.2.1

[yuezk]

gpservice is supposed to be run as root because connect the VPN needs the root permission.

[timp87]

No doubt. But it should not just crash.