test_fiber.rb: fix test_create_fiber_in_new_thread
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63081 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_fiber.rb: fix test_create_fiber_in_new_thread
prefix to run, and get the result value not only waiting.
[Bug #14642]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63081 b2dd03c8-39d4-4d8f-98ff-823fe69b080e