Remove some more unnecessary code.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc8.0.x/trunk@1645642 13f79535-47bb-0310-9956-ffa450edef68
Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=57326
Enable AsyncListeners to re-register themselves through AsyncListener.onStartAsync ()

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc8.0.x/trunk@1645686 13f79535-47bb-0310-9956-ffa450edef68