GCP provisioning can fail with 412

[cg505]

In our GCP project, we have a tool that may set the labels of a newly-created VM. This can cause GCP provisioning to fail:

D 01-16 01:37:59 provisioner.py:153] googleapiclient.errors.HttpError: <HttpError 412 when requesting https://compute.googleapis.com/compute/v1/projects/sky-dev-465/zones/us-east4-b/instances/a-37-20ae-head-efep8jh1-compute/setLabels?alt=json returned "Labels fingerprint either invalid or resource labels have changed". Details: "[{'message': 'Labels fingerprint either invalid or resource labels have changed', 'domain': 'global', 'reason': 'conditionNotMet', 'location': 'If-Match', 'locationType': 'header'}]">

This is retryable, we just need to fetch the new labels from GCP and re-add the labels we are trying to set.