Update buildfarm deployment logic because of groovy v2 changes

[mikaelarguedas]

• install diffutils from here to /var/lib/jenkins/plugins/groovy/WEB-INF/lib/
• create a scriptApproval.xml file (referencing all scripts and methods allowed for groovy scripts to run) in /var/lib/jenkins. Content of this file at the time of the writing is here

replaces ros-infrastructure/ros_buildfarm#419

[dirk-thomas]

Please use the current approval list from Jenkins which has been updated since the creation of the gist (and will continue to be updated).

[nuclearsandwich]

It isn't part of the current xenial refactor, but I think the long term way to handle this will be to write a script which fetches the the current production script approval settings and generates a Groovy script to set the same script approval settings via puppet on newly configured buildfarms.

This will likely need to happen for #42 which is on deck after the migration.