Major Description
In order to better align with the OOTB DEMO LDAP config in gateway-site.xml, we should have the whitelist explicitly set for demo environments which is best assumed to be the variants of localhost that may be used in demo and dev environments.
Rather than spread this config across topologies, we should include this in gateway-site.xml by default as well. This will allow the LDAP and whitelist configurations to be changed to production scenarios in the same place. Also, gateway-site.xml is manageable by Ambari while not all topologies are.