post-processor/docker-push: drop unused test helper functions (#8456)
post-processor/docker-push: drop unused test helper functions (#8456)


timsutton/packer,hashicorp/packer,dave2/packer,ricardclau/packer,rnaveiras/packer,rnaveiras/packer,timsutton/packer,ricardclau/packer,pecigonzalo/packer,paulmey/packer,grubernaut/packer,ricardclau/packer,rnaveiras/packer,timsutton/packer,rnaveiras/packer,dave2/packer,dave2/packer,mitchellh/packer,hashicorp/packer,paulmey/packer,paulmey/packer,grubernaut/packer,timsutton/packer,mitchellh/packer,mitchellh/packer,paulmey/packer,timsutton/packer,grubernaut/packer,dave2/packer,grubernaut/packer,mitchellh/packer,pecigonzalo/packer,ricardclau/packer,timsutton/packer,ricardclau/packer,dave2/packer,paulmey/packer,grubernaut/packer,ricardclau/packer,hashicorp/packer,paulmey/packer,pecigonzalo/packer,mitchellh/packer,rnaveiras/packer,hashicorp/packer,dave2/packer,pecigonzalo/packer,rnaveiras/packer,grubernaut/packer