fix: remove extraneous log output wrt stopping icx-proxy

[ghost]

When dfx starts, it logs "Stopping icx-proxy..." "Stopped" when it didn't actually do that.

[jwiegley]

Would this perhaps be any clearer?

    fn stop_icx_proxy(&mut self) {
        if let Some(sender) = self.stop_sender.take() {
            info!(self.logger, "Stopping icx-proxy...");
            sender.send(()).unwrap();
            info!(self.logger, "Stopped.");
        } else if let Some(join) = self.thread_join.take() {
            info!(self.logger, "Stopping icx-proxy...");
            join.join().unwrap();
            info!(self.logger, "Stopped.");
        }
    }

[ghost]

No, the normal case is that both are Some, and the stop sequence is:

1. signal the handler thread to stop (sender.send())
2. wait for handler thread to exit (join.join())