Print job progress in load job examples. (#5566)
Print job progress in load job examples. (#5566)

This aligns the load job BigQuery samples with the Cloud DPE sample
rubric guidelines and makes it easier to align samples across languages.
tswast/google-cloud-python,tseaver/google-cloud-python,GoogleCloudPlatform/gcloud-python,jonparrott/gcloud-python,GoogleCloudPlatform/gcloud-python,dhermes/gcloud-python,tseaver/google-cloud-python,tseaver/gcloud-python,tswast/google-cloud-python,jonparrott/google-cloud-python,googleapis/google-cloud-python,dhermes/google-cloud-python,dhermes/gcloud-python,tseaver/google-cloud-python,googleapis/google-cloud-python,jonparrott/google-cloud-python,dhermes/google-cloud-python,tseaver/gcloud-python,dhermes/google-cloud-python,tswast/google-cloud-python,jonparrott/gcloud-python