fake_pathlib's resolve() does not reproduce error when path has file ancestor

Under Python 3.6:

```python
>>> p = pathlib.Path('/path/to/file/this can not exist')
>>> p.resolve()
Traceback (most recent call last):
  ...
NotADirectoryError: [Errno 20] Not a directory: '/path/to/file/this can not exist'
```

`pyfakefs.fake_pathlib.FakePath.resolve()` does not raise an exception.