Upgrade puppetlabs/apt to 1.4.2

https://github.com/puppetlabs/puppetlabs-apt/compare/1.4.0...1.4.2

Mainly there is a bug in the sources.list.erb file which prevents us
adding a new repo.
Add azul::repo

We would like to try out Zulu OpenJDK 8. This is a first step towards
that.
Merge pull request #526 from alphagov/feature/azul-repo

Add Azul apt repo