xfs support in test_rename_directory_to_non_empty_directory

Seemingly on XFS only, the `AlreadyExists` variant is returned.

Reproducible on Linux hosts:

```rust
use clap::Parser;

struct Args {
    /// Destination to try
    #[arg()]
    path: std::path::PathBuf,
}

fn main() {
    let args = Args::parse();

    // Renaming a directory over a non-empty existing directory should fail.
    let tmpdir = std::path::Path::new(&args.path);
    std::fs::create_dir_all(tmpdir).unwrap();

    let source_path = tmpdir.join("source_directory");
    let target_path = tmpdir.join("target_directory");

    std::fs::create_dir(&source_path).unwrap();
    std::fs::create_dir(&target_path).unwrap();

    let target_path_file = target_path.join("target_file.txt");
    std::fs::write(target_path.join("target_file.txt"), b"target hello world").unwrap();
    println!("wrote {target_path_file:?}");

    println!("{source_path:?} -> {target_path:?}");
    let err = std::fs::rename(source_path, target_path).unwrap_err();
    assert_eq!(err.kind(), std::io::ErrorKind::DirectoryNotEmpty);
}
```

```bash
XFS_BLOCK=image-xfs
truncate -s 512M image-xfs
mkfs.xfs -q image-xfs
mkdir mnt-xfs
sudo mount -o loop image-xfs mnt-xfs
sudo chmod 777 mnt-xfs
cargo run -- mnt-xfs/
```

Output:

```
wrote "mnt-xfs/target_directory/target_file.txt"
"mnt-xfs/source_directory" -> "mnt-xfs/target_directory"

thread 'main' (267220) panicked at src/main.rs:30:5:
assertion `left == right` failed
  left: AlreadyExists
 right: DirectoryNotEmpty
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```