workaround for some tests where race codition causes erl output to not flush

an example output: <del>https://github.com/elixir-lang/elixir/issues/1280#issuecomment-21693200</del>
EDIT: this: https://github.com/elixir-lang/elixir/issues/1280#issuecomment-21118074

view it with this: https://github.com/elixir-lang/elixir/pull/1515/files?w=1
aka "?w=1" to the url