cleanup logging on shutdown

git-svn-id: https://svn.apache.org/repos/asf/archiva/trunk@1549732 13f79535-47bb-0310-9956-ffa450edef68
add comment on logging mechanism

git-svn-id: https://svn.apache.org/repos/asf/archiva/trunk@1549733 13f79535-47bb-0310-9956-ffa450edef68