Unnecessary recursive creation of catalogs with workflow

When path is relative vs absolute. Reported by @christineecker, thanks!

command that was used on a datalad dataset `superset` with one subdataset `subset`:

```
datalad catalog-workflow --mode new --catalog myCat --dataset superset --extractor metalad_core
```

When the `myCat` was changed to an absolute path, the recursive catalog creation didn't happen.



