Improved resource management by File backed non-blocking entities

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1480298 13f79535-47bb-0310-9956-ffa450edef68
Fixed resource leak warnings in test cases

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1480299 13f79535-47bb-0310-9956-ffa450edef68