add folder and publish configuratio to upload rosdistro_cache

I have already applied both changes to the running EC2 farm:

* http://ec2-54-67-30-249.us-west-1.compute.amazonaws.com:8080/view/Manage/job/indigo_rosdistro_cache/
* http://ec2-54-67-51-1.us-west-1.compute.amazonaws.com/rosdistro_cache/
This directory needs to be create first. It needs a dependency on File['/var/repos'] like: https://github.com/ros-infrastructure/buildfarm_deployment/blob/master/repo/manifests/site.pp#L135