Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56472#c1

Per my comment on that issue, always set 'NamingContextListener.initialized' field to 'true'
so that its cleanup on configure_stop event is not skipped.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1593356 13f79535-47bb-0310-9956-ffa450edef68