Close pipes.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46258 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/testunit/test_parallel.rb

@@ -32,6 +32,9 @@ module TestParallel
           end
         end
       end
+    ensure
+      @worker_in.close
+      @worker_out.close
     end
 
     def test_run