os-hosts CLIs and python API bindings had been deprecated from
python-novaclient 9.0.0 and finally became removed in 10.0.0 release.
The related scenarios become redundant. We cannot launch then in gates
and it is impossible to ensure that they work even with old novaclient
release. Since it is not something critical and what is called regulary
in old OpenStack environments we should not provide any workaround and
can just remove the os-hosts logic from Rally.
[*] https://github.com/openstack/python-novaclient/blob/master/releasenotes/notes/remove-hosts-d08855550c40b9c6.yaml
Change-Id: I915983dbc634dafcab1cc54dba7bae8d4e368884
1efddbd5ba