OpenStack - Ensure inventory is collected for all tenants.

@Fryguy @blomquisg please review.

For OpenStack refresh, ensure inventory is collected for all of the
tenants the EMS can access.

Extended OpenstackHandle to include tenant iterators.
Updated EmsOpenstack and the openstack parser to use the OpenstackHandle accordingly.
Updated spec tests and rerecorded vcr cassettes.
"delegate" wouldn't be accurate. As you point out, this is the "delegated" object, not the delegate (which is the object being instantiated). I would consider calling it "delegated" or "delegated_obj", as "delegated" might be taken for a Boolean. Still seems a bit much to me. The definition of the Delegate class calls this "obj" and it didn't confuse me. :-)