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.
Looks like the `$fog_log` instrumentor was removed here.  Unless we want to completely do away with the fog log, I think this should conditionally set the `:instrumentor` option to `$fog_log` if it's not already set by `extra_opts`.