MBeans descriptions are not loaded in JMX for ModClusterListener

Several problems:

1. we need to support org.jboss.modcluster.container.tomcat.ModClusterListener and org.jboss.modcluster.container.catalina.standalone.ModClusterListener at the same time
2. name of the beans-destriptors file is now wrong, since i followed the description at https://tomcat.apache.org/tomcat-7.0-doc/mbeans-descriptor-howto.html which is totally incorrect, those resources are not loaded! (PR to Apache shortly)