work around TAP stream pollution on circleci
work around TAP stream pollution on circleci

The test passes on circleci if I ssh into circle,
but it fails when run unattended. I suspect this is because
circleci cannot remove container layers (`--rm`) due to
security restrictions, and the output clutters the output
collected in `${lines}`.

jumanjihouse/puppet-on-coreos,jumanjiman/puppet-on-coreos