Fix country detection from QLocale

Summary:
Neither QLocale::name() nor QLocale::bcp47Name() return a country
ISO code, as it was expected here.

Adapt the unit test to cover the interesting case of multi-lingual
countries for this.

Reviewers: dvratil

Reviewed By: dvratil

Subscribers: kde-pim

Tags: KDE PIM

Differential Revision: https://phabricator.kde.org/D13942