Fix a segmentation fault in autotest messagefactoryngtest

Summary:
Messagefactoryngtest usually fails due to a segmentation fault.  The
fault happens most often during initTestCase at the call to
ident.uoid(), but sometimes occurs at other spots.

This patch avoids the fault.  It imitates the initialization pattern
in templateparserjobtest.

Reviewers: dvratil

Reviewed By: dvratil

Subscribers: dvratil, kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D22779