Should be invocable as a dynamic inventory

[Bogdan Dobrelya]

It should be working if invoked with the commands like "ansible -i ./shade-inventory --list-hosts all".
It should preserve the data path backwards compatible with the JSON output provided by the "standard" openstack.py dynamic inventory, which is store all data fetched under the { "openstack": "<...>" } dict. Otherwise, systems cannot easily migrate from the GPL openstack.py to shade-inventroy, because of the data paths like "openstack.metadata/openstack.private_v4/openstack.public_v4" are missing.