Add link to Ubuntu cloud archive documentation.
Add link to Ubuntu cloud archive documentation.

Change-Id: Icfefac9e47776f32001309b5df0a376694640066

kairoaraujo/openstack-manuals,saeki-masaki/openstack-manuals,saeki-masaki/openstack-manuals,Akasurde/openstack-manuals,potsmaster/openstack-manuals,kairoaraujo/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,gongysh2004/openstack-manual,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,gongysh2004/openstack-manual,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,Akasurde/openstack-manuals,potsmaster/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals