CppunitTest_sw_ooxmlexport: restore this test

It was crashing, as a quick-fix 43feacd5330b5652b58e8a75a0f41a78ee6ebe1c
(sw: fix build, 2014-02-08) disabled the test. I wanted to fix this
properly today, but it was already working.

Change-Id: Ifbfa82bc907d6c4bd8ec398472f751714c721b09