really fix tests that fail when older [MakeMaker] is installed, that has a eumm_version default

e.g. http://www.cpantesters.org/cpan/report/02295137-6bfd-1014-965f-21666eb11bd9
Dist-Zilla-Plugin-MakeMaker-Fallback-0.013

          - fix test from previous release's fix that was incompatible with
            earlier versions of [MakeMaker]'s practice of always setting
            eumm_version