ap_discard_request_body: exit without reading the body if

connection->keepalive is false.  This works in conjunction with
ap_die which resets connection->keepalive any time
ap_status_drops_connection is true.  The latter is explicity tested
here in case ap_die isn't involved.

Submitted by:   Justin Erenkrantz, Greg Ames


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@95882 13f79535-47bb-0310-9956-ffa450edef68