Improved resource management by File backed async consumers / producers

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1480278 13f79535-47bb-0310-9956-ffa450edef68
Suppress resource leak warning for HttpClientExchangeHandler instances

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpasyncclient/trunk@1480281 13f79535-47bb-0310-9956-ffa450edef68