test-mime-data: fail when an error occurs

This change should prevent test file omissions like the one fixed in shared-mime-info@66c73d06

Always print summary. The condition (error > 0 || failed > 0) was incomplete: xmatch > 0 should have been checked as well. shared-mime-info's test_mime.sh passes a list with many expected failures to test-mime-data, so the condition failed > 0 is always true. Therefore printing the summary unconditionally makes no difference, unless there are other users of test-mime-data that don't have expected failures in their test case lists.