[#52858717] support for running puppet tests

We will want to run tests as we add the code that sets up the
jenkins user to talk to git etc. This should allow this project
to support that
[#52858717] add git the ci-master box

we want git on the ci master so we can communicate to github
Merge pull request #17 from alphagov/back_up_jenkins_config

First steps to set up Git connectivity on the CI boxes