We only run expand-groups.sh during launch-node -- which makes sense
for additions as we don't have hosts appearing that don't come via
that path. However nothing really runs it on removal of hosts,
meaning /etc/ansible/hosts/generated-groups can contain old entries
until the next time a new host is launched. Simply run it once a day
to keep it fresh.
[1] http://git.openstack.org/cgit/openstack-infra/system-config/tree/launch/launch-node.py#n172
Change-Id: Ia112082df33b5ebf465f7d5a23685cc3e28b0551