Add tests for StepCopyFiles.
Add tests for StepCopyFiles.

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