mpm_{worker,prefork}: save some cycles by not copying the listener's pollfds

for each pollset operation.

We don't need a copy when poll()ing if those are allocated with the correct
lifetime (the listener thread) at the very beginning.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1662437 13f79535-47bb-0310-9956-ffa450edef68