Use list_concat for metadata_settings for haproxy
Use list_concat for metadata_settings for haproxy

Change-Id: Ia0e0a12e1863dce657d4e1c7f9894ea5bfd008be

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates,dprince/tripleo-heat-templates,dprince/tripleo-heat-templates