r63236 (or r63237) introduces test failures and CI shows errors.
This commit makes skipping these tests. Please revert this commit
after tests (and rubyspec) work fine.
Failure log example:
https://gist.github.com/ko1/8456cf25fe35a696bd33ac86135092e4
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63239 b2dd03c8-39d4-4d8f-98ff-823fe69b080e