HTTPCLIENT-1290: 304 cached response never reused with If-modified-since conditional requests
Contributed by Francois-Xavier Bonnet <francois-xavier.bonnet at centraliens.net>

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/branches/4.2.x@1430247 13f79535-47bb-0310-9956-ffa450edef68