event: always favor APR_POLLSET_WAKEABLE over method/implementation.

(probably more about correctness than a real issue since systems are
unlikely to implement more than one/their method...).


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1835846 13f79535-47bb-0310-9956-ffa450edef68