[Reviewer: Alex] Rely on common ralf/Homestead script to create freeDiameter config file

Can you review alongside https://github.com/Metaswitch/clearwater-infrastructure/pull/70?

Fixes https://github.com/Metaswitch/ralf/issues/61, fixes https://github.com/Metaswitch/ralf/issues/35, fixes https://github.com/Metaswitch/chef/issues/120.

This changes Ralf's default port to 3869, but I assert that this is a non-breaking change, as nothing ever connects in to the CTF.