HTTPCLIENT-1311: made sure the current thread is re-interrupted if InterruptedException is caught and re-thrown as a different exception; tweaked connection manager API related to interruptable operations

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1441414 13f79535-47bb-0310-9956-ffa450edef68