event: follow up to r1762718.

On graceful shutdown/restart, kill kept-alive connections before poll()ing
again, avoiding to wait for their "normal" timers (before being woken up)
when they remain the last handled connections.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1774538 13f79535-47bb-0310-9956-ffa450edef68