Document resource leak warning

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/fileupload/trunk@1568660 13f79535-47bb-0310-9956-ffa450edef68
Fix potential resource leak

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/fileupload/trunk@1568661 13f79535-47bb-0310-9956-ffa450edef68