cloud-init-nocloud element for non-cloud image

Disables cloud-init from querying EC2 metadata, or any cloud metadata
service. It keeps only the Nocloud and None data sources, which are both
expected to be "baked in" to an image.  This speeds up boot by 2 minutes
on hosts where cloud-init cannot reach the EC2 metadata service.

Change-Id: I43522c4a442c0f2fc2044d4898768ceb4f839099
Merge "cloud-init-nocloud element for non-cloud image"