Added inventory collection for OpenStack cloud storage.

Added collection of: volumes, volume snapshots, object store containers and object store objects.
Rubocop cleanup.
Check for nil arg passed to link_volumes_to_base_snapshots method.
Fixed issues uncovered by spec tests.
Fixed CloudVolume spec.

Accounting for the fact that cloud volumes are now connected to
VMs through disks, as opposed to directly.
Rebased cloud_storage to master

Updated cloud storage code to use tenant updates of OpenstackHandle.
Rubocop clean up.
Merge pull request #129 from roliveri/cloud_storage

Added inventory collection for OpenStack cloud storage.