Cache does no longer send Content-Type header

for fresh content.

Followup to r1361153+r1373447 (PR 53539, wrong
Content-Type for stale content).


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1439083 13f79535-47bb-0310-9956-ffa450edef68