Puppet installation needs an 'apt-get update'

The puppetlabs-release-${DISTRIB_CODENAME}.deb provides the GPG key and /etc/apt/sources.list.d/puppetlabs.list for the Puppetlabs repository.
Without a proper 'apt-get update' the Puppetlabs packages are not loaded.
Merge pull request #33 from dol/patch-2

Puppet installation needs an 'apt-get update'