On a server that is not Enterprise the Tenants page is still only the
notice. On Enterprise the notice is gone -- a real installation that has
tenants has the licence -- unless SHOW_ENTERPRISE_NOTICES=1 asks for it above
the list. The public demo will set it: it reports Enterprise so tenants can be
shown, and should not suggest they come without the licence. The setting
reaches the browser as session.ihasmail.server.enterpriseNotices.