Type error when using `max_calls` in the autopopulate function

The argument `max_calls` in the autopopulate function added in https://github.com/datajoint/datajoint-python/commit/7299058ee37c44216a5a53acbcb737d68f47fdc4 throws a type error:

```
--> 126             if max_calls is not None and call_count >= max_calls:
    127                 break

TypeError: unorderable types: itertools.count() >= int()
```