Fix getting last modified for tagfiles in JAR so that it is not marked as not found. I chose to not fix and use getResource in that case (it looked slower to go through the URL since the point is to avoid using JAR URLs I suppose), but this could need fixing too just in case it is used.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1550823 13f79535-47bb-0310-9956-ffa450edef68