Fix truncated output in `fig run` - resolves #658

Signed-off-by: Michael Malet <MichaelMa@square-enix.com>
Ah ok, that makes more sense. I took another look at it, and it feels like it should be possible to implement this without `dockerpty`, and use the `container.attach()` instead (so that we can preserve the options). I didn't have any luck getting that working though.