Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56736
Avoid incorrect ISE if the timeout fires after a non-container thread has called dispatch() but before a container thread processed the dispatch()

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1616452 13f79535-47bb-0310-9956-ffa450edef68