https://issues.apache.org/bugzilla/show_bug.cgi?id=56546 (very partial)
Reduce verbosity of clear references logging. Although it is a good tool for detecting leaks, the severity does not match the likely impact. Also avoid having more than one logging for one event even if filtering becomes less flexible.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1602159 13f79535-47bb-0310-9956-ffa450edef68