Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=55656
Configure the Digester to use the server class loader when parsing server.xml rather than the class loader that loaded StandardServer.
Patch provided by Roberto Benedetti.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1533119 13f79535-47bb-0310-9956-ffa450edef68