Mark mozilla tests as flaky instead of failing

Apparently, they work on windows

BUG=v8:2893
TBR=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/23583046

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16787 ce2b1a6d-e550-0410-aec6-3dcde31c8c00