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.
I'll have to give this some thought. The intent here was to mimic the behavior of the old connect method - as to not impact existing code that was not being changed at this time. I think option 2 could be implemented without breaking anything.