Lubuntu: Fix GeoIP parsing
Summary:
With the recent switch of the GeoIP service, the format has also changed from
JSON to XML. This was not correctly changed in the welcome module for Lubuntu.
Test Plan:
- Start Calamares (e.g. with an IP address from Europe).
- Check, that the language is set correctly (e.g. French when in France).
Reviewers: wxl, tsimonq2, kc2bez
Reviewed By: wxl, kc2bez
Differential Revision: https://phab.lubuntu.me/D101