leakchecker.rb: MiniTest::Unit.output

* test/lib/leakchecker.rb (LeakChecker#puts): send output to
  MiniTest::Unit.output, not to be mixed with parallel test
  commands.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46654 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_io.rb: fix leaked threads

* test/ruby/test_io.rb (test_readpartial_locktmp): ensure reading
  thread is dead to fix leaked threads.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46655 b2dd03c8-39d4-4d8f-98ff-823fe69b080e