Merge r1669289, r1669292 from trunk:

core_filters: restore/disable TCP_NOPUSH option after non-blocking sendfile.

CHANGES: follow up to r1669289.
Submitted by: ylavic
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1670328 13f79535-47bb-0310-9956-ffa450edef68