test/lfs-openat: open dfd with O_PATH
This triggers a bug present until at least Linux 5.6.11, causing
EBADF, see
@@ -78,7 +78,7 @@ static int prepare_file(int dfd, const char* fn)
int main(int argc, char *argv[])
{
const char *fn = "io_uring_openat_test";
- int dfd = open("/tmp", O_RDONLY | O_DIRECTORY);
+ int dfd = open("/tmp", O_PATH);
struct io_uring ring;
int ret;
