. fix ruby-libvirt library require name (libvirt)
Merge pull request #2860 from noushi/libvirt-fix_missing_tests

. fix ruby-libvirt library require name (libvirt)
[google|compute] Update Images support

- Add missing "Image" properties
- Add "ready?" method to model
- Add "destroy" method to model
- Use "Operation" instead of the "backoff_if_unfound" method when inserting an "Image"