core: don't send EOR bucket through request filters.

The core request filter is the only one which should take care of it.
In theory the other request filters should have bailed out on EOS already,
but that's not always the case (and even less the case on error).
So be safe by not sending them a bucket which may destroy the request (and
their brigade) underneath them.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1822600 13f79535-47bb-0310-9956-ffa450edef68