selftests/bpf: Use start_server_str in test_tcp_check_syncookie_user

Since start_server_str() is added now, it can be used in script
test_tcp_check_syncookie_user.c instead of start_server_addr() to
simplify the code.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Link: https://lore.kernel.org/r/5d2f442261d37cff16c1f1b21a2b188508ab67fa.1718932493.git.tanggeliang@kylinos.cnSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/test_tcp_check_syncookie_user.c

@@ -156,10 +156,6 @@ static int v6only_false(int fd, void *opts)
 int main(int argc, char **argv)
 {
 	struct network_helper_opts opts = { 0 };
-	struct sockaddr_in addr4;
-	struct sockaddr_in6 addr6;
-	struct sockaddr_in addr4dual;
-	struct sockaddr_in6 addr6dual;
 	int server = -1;
 	int server_v6 = -1;
 	int server_dual = -1;
@@ -181,36 +177,17 @@ int main(int argc, char **argv)
 		goto err;
 	}
 
-	memset(&addr4, 0, sizeof(addr4));
-	addr4.sin_family = AF_INET;
-	addr4.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
-	addr4.sin_port = 0;
-	memcpy(&addr4dual, &addr4, sizeof(addr4dual));
-
-	memset(&addr6, 0, sizeof(addr6));
-	addr6.sin6_family = AF_INET6;
-	addr6.sin6_addr = in6addr_loopback;
-	addr6.sin6_port = 0;
-
-	memset(&addr6dual, 0, sizeof(addr6dual));
-	addr6dual.sin6_family = AF_INET6;
-	addr6dual.sin6_addr = in6addr_any;
-	addr6dual.sin6_port = 0;
-
-	server = start_server_addr(SOCK_STREAM, (struct sockaddr_storage *)&addr4,
-				   sizeof(addr4), NULL);
+	server = start_server_str(AF_INET, SOCK_STREAM, "127.0.0.1", 0, NULL);
 	if (server == -1)
 		goto err;
 
 	opts.post_socket_cb = v6only_true;
-	server_v6 = start_server_addr(SOCK_STREAM, (struct sockaddr_storage *)&addr6,
-				      sizeof(addr6), &opts);
+	server_v6 = start_server_str(AF_INET6, SOCK_STREAM, "::1", 0, &opts);
 	if (server_v6 == -1)
 		goto err;
 
 	opts.post_socket_cb = v6only_false;
-	server_dual = start_server_addr(SOCK_STREAM, (struct sockaddr_storage *)&addr6dual,
-					sizeof(addr6dual), &opts);
+	server_dual = start_server_str(AF_INET6, SOCK_STREAM, "::0", 0, &opts);
 	if (server_dual == -1)
 		goto err;