Trusted network CIDR would best be an Array

[miguelaferreira]

This way we can better integrate with other tools (like kitchen e.g.).

[bheuvel]

When using the latest PR created at kitchen-vagrant test-kitchen/kitchen-vagrant#167 ;

   pf_trusted_networks:
      - "a.a.a.a"
      - "b.b.b.b"

resulting/requested Vagrantfile:

pf_trusted_network = ["a.a.a.a", "b.b.b.b"]