Cache creates error

In `sync.py` on the last line of the code below, the code can try to create a directory of the same name as an existing file:
```python
# Create cfile in in-progress_dir
    if not cfile.in_progress.is_dir():
        if not get_option('dry_run', cfile, cfile.device):
            os.mkdir(cfile.in_progress)
```

Perhaps filetailor should clean the cache when this happens?