Use a single event for the lifetime of the 'AcceptFilter none' variety

sockets; it appears that resetting the accept event while another was 
waiting would break the pending connection, causing host socket resets.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@750567 13f79535-47bb-0310-9956-ffa450edef68