selftests/bpf: test_progs: Don't leak server_fd in tcp_rtt

server_fd needs to be closed if pthread can't be created.

Fixes: 8a03222f ("selftests/bpf: test_progs: fix client/server race in tcp_rtt")
Signed-off-by: NBrian Vazquez <brianvv@google.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Reviewed-by: NStanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20191001173728.149786-2-brianvv@google.com

tools/testing/selftests/bpf/prog_tests/tcp_rtt.c

@@ -260,13 +260,14 @@ void test_tcp_rtt(void)
 
 	if (CHECK_FAIL(pthread_create(&tid, NULL, server_thread,
 				      (void *)&server_fd)))
-		goto close_cgroup_fd;
+		goto close_server_fd;
 
 	pthread_mutex_lock(&server_started_mtx);
 	pthread_cond_wait(&server_started, &server_started_mtx);
 	pthread_mutex_unlock(&server_started_mtx);
 
 	CHECK_FAIL(run_test(cgroup_fd, server_fd));
+close_server_fd:
 	close(server_fd);
 close_cgroup_fd:
 	close(cgroup_fd);