minor improvement

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1440605 13f79535-47bb-0310-9956-ffa450edef68
minor improvement: remove unused logger field

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1440606 13f79535-47bb-0310-9956-ffa450edef68