[google|compute] Some fixes for Images

- Fix insert_image request body (add 'source' Hash to 'rawDisk')
- Fix reload image to add the project to the properties
Merge pull request #2882 from frodenas/gce_images

[google|compute] Some fixes for Images
[google|compute] Improve Server support

- Allow can_ip_forward option when creating a server
- Allow not to allocate an external IP when creating a server
- Use "Operation" instead of the "backoff_if_unfound" method when creating a server