Allow ap_discard_request_body to be called multiple times in the

same request.  Essentially, ap_http_filter keeps track of whether
it has sent an EOS bucket up the stack, if so, it will only ever
send an EOS bucket for this request.

Submitted by:	Ryan Bloom, Justin Erenkrantz, Greg Stein


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@95505 13f79535-47bb-0310-9956-ffa450edef68