MINOR: connection: use conn_fd() when displaying connection errors

The SSL connection errors and socks4 proxy errors used to blindly dump
the FD, now it's sanitized via conn_fd().

src/connection.c

@@ -1404,7 +1404,7 @@ int conn_send_socks4_proxy_request(struct connection *conn)
 				(conn->subs && conn->subs->events & SUB_RETRY_SEND) ? CO_SFL_MSG_MORE : 0);
 
 		DPRINTF(stderr, "SOCKS PROXY HS FD[%04X]: Before send remain is [%d], sent [%d]\n",
-				conn->handle.fd, -conn->send_proxy_ofs, ret);
+			conn_fd(conn), -conn->send_proxy_ofs, ret);
 
 		if (ret < 0) {
 			goto out_error;

src/ssl_sock.c

@@ -620,7 +620,7 @@ static forceinline void ssl_sock_dump_errors(struct connection *conn)
 			if (ret == 0)
 				return;
 			fprintf(stderr, "fd[%#x] OpenSSL error[0x%lx] %s: %s\n",
-			        conn->handle.fd, ret,
+			        conn_fd(conn), ret,
 			        func, ERR_reason_error_string(ret));
 		}
 	}