add config prepare tests
add config prepare tests

rnaveiras/packer,pecigonzalo/packer,mitchellh/packer,pecigonzalo/packer,ricardclau/packer,mitchellh/packer,hashicorp/packer,rnaveiras/packer,rnaveiras/packer,ricardclau/packer,mitchellh/packer,rnaveiras/packer,mitchellh/packer,hashicorp/packer,hashicorp/packer,pecigonzalo/packer,pecigonzalo/packer,ricardclau/packer,rnaveiras/packer,mitchellh/packer,ricardclau/packer,ricardclau/packer,hashicorp/packer,rnaveiras/packer,ricardclau/packer