OAK-497: No LoginModules configured error on Java 7

Drop severity of the default JAAS configuration messages from warn to info,
as they simply state that in the absense of explicit JAAS configuration the
default built-in configuration gets used.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1435139 13f79535-47bb-0310-9956-ffa450edef68