Fix default vrf static routes issue

[loulecrivain]

fixes #89

TODO:

• config file default VRF name parameter
  in json schema spec and settings
• remove logic branch where field is expected
  to be nullable and/or fail on null ("illegal" value)
• by-manufacturer default VRF path "spit with"
  (same as interface ?) should be moved in
  manufacturer in any case
  • routing_options for ansible_junos
  • routing_instances.default for rtbrick
• update / fix test cases, 1 by manufacturer
• rebase after validate cosmo configuration file with JSON schema #108 is merged

[n0emis]

This currently generates a change to all generated config files with the nix output, since it reorders the isis config option. but I don't think that this is a blocker