Also two points...
1. You can directly add the public IP in Gluu Server container's hosts file ( log into container with 'service gluu-server login' and add this in /etc/hosts.
2. You can call the Gluu Server logout link ( https://<hostname>/idp/logout.jsp ) from SP instead of providing SP's logout link in Trust relationship.
#2 is famous among our customers as they have various types of SPs out there ( in-house, SaaS, remote ).