fix some package installation issues

* package_installed? must check for 'ii' status (resolvconf was
  in 'uc' state, probably as a leftover from building the box )
* debconf may ask questions even with DEBIAN_FRONTEND=noninteractive
  if certain options aren't set (puppet packages couldn't be
  configured if a modified version of /etc/puppet/puppet.conf was
  already installed)
Implement load-balancing over puppetdb instances (issue #1)