merge revision(s) 52222,52229,52273,52277,52357: [Backport #11613]
limit the number of FDs in a process for stress test
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@52779 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 52222,52229,52273,52277,52357: [Backport #11613]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@52779 b2dd03c8-39d4-4d8f-98ff-823fe69b080e