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.
It should be set in a central place, but it has to be set to a consistent value. The fact that the value differs between Travis and local runs is more than annoying, it can result in a tremendous waste of time.
Given the code in spec_helper.rb, this line in the pr will only effect local test runs, not Travis.
I can remove it, but I think the way it's being set now is a big problem.