test_minitest_unit.rb: fix "random" sort
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54975 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_minitest_unit.rb: fix "random" sort
hack to fix the order by avoiding duplicate keys.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54975 b2dd03c8-39d4-4d8f-98ff-823fe69b080e