fix renaming issue

[DirkEilander]

Issue addressed

Fixes #881

Explanation

Variables on datasets with only a single variable were not checked. The reason was that we want to automatically convert variable names from tif files (which get the file name as variable by default) if a variable is requested. This is important to make sure we can still read tif files based on the path if not set in the data catalog without getting errors on the variable name. I have moved this functionality to the raster driver and now make sure the check for variables always occurs.

Checklist

• Updated tests or added new tests
• Branch is up to date with main
• Tests & pre-commit hooks pass
• Updated documentation if needed
• Updated changelog.rst if needed
• For predefined catalogs: update the catalog version in the file itself, the references in data/predefined_catalogs.yml, and the changelog in data/changelog.rst

Additional Notes (optional)

@Jaapel this behaviour should also land in #857

[hboisgon]

Works like a charm!