Fix MaxRequestsPerChild on the Event MPM. It hasn't worked for 4 years.

* server/mpm/experimental/event/event.c
    (process_socket): Be consistent about our return value, returning 0
      means this connection is done, and that we can decrement requests_this_child.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@719357 13f79535-47bb-0310-9956-ffa450edef68