Follow-up to r1635154.
When scanning the class path, exclude WEB-INF/classes if it has already been scanned and exclude JARs from WEB-INF/lib that have been scanned.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1635449 13f79535-47bb-0310-9956-ffa450edef68