[BUG] CVATImageDataset Importer is not working for data stored in a connected file share

CVAT allows users to connect a file share containing the media to annotate. When this is used, the paths stored in the exported XML cause issues when imported into FiftyOne with the following:

```python
import fiftyone as fo

name = "my-dataset"
dataset_dir = "/path/to/cvat-image-dataset"

# Create the dataset
dataset = fo.Dataset.from_dir(
dataset_dir=dataset_dir,
dataset_type=fo.types.CVATImageDataset,
name=name,
)
```

The exact error is TBD