Ignore source image updates

[kolja71]

This lifecycle block tells Terraform to ignore changes to the listed attributes on the VM resource, so plan/apply will not try to update or replace the VM if those attributes differ from state.

• "tags": prevents Terraform from changing (or forcing updates for) tag diffs on the VM.
• "source_image_id": prevent Terraform from attempting to update or recreate the VM when the image id changes (covers a custom image id).

Consequence: external/manual changes to tags or to the VM image will be skipped by Terraform (changes must be managed outside Terraform or by removing the ignore).