Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56536
Ensure that HttpSessionBindingListener.valueUnbound() uses the correct class loader when the <code>SingleSignOn</code> valve is used.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1595285 13f79535-47bb-0310-9956-ffa450edef68