Merge r1001884 from trunk:

mod_cache: Make sure that we never allow a 304 Not Modified response
that we asked for to leak to the client should the 304 response be
uncacheable. PR45341

Submitted by: minfrin
Reviewed by: minfrin, jim, covener


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1068313 13f79535-47bb-0310-9956-ffa450edef68