Make gce_instance example show how to use a service account
Make gce_instance example show how to use a service account

ihmccreery/puppetlabs-gce_compute,icg-puppet/puppetlabs-gce_compute,icg-puppet/puppetlabs-gce_compute,puppetlabs/puppetlabs-gce_compute,puppetlabs/puppetlabs-gce_compute,hunner/puppetlabs-gce_compute,ihmccreery/puppetlabs-gce_compute,hunner/puppetlabs-gce_compute