Fix failing tests due to IAP communicator host name
Fix failing tests due to IAP communicator host name

Moved setting the host from ApplyIAPTunnel to Config.Prepare but forgot to
update the related tests.

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