mpm_event: Simplify pollset "good methods" vs APR_POLLSET_WAKEABLE.

mpm_event: Simplify pollset "good methods" vs APR_POLLSET_WAKEABLE.

* server/mpm/event/event.c(setup_threads_runtime):
  Simplify pollset creation code.

All pollset "good methods" implement APR_POLLSET_WAKEABLE and wake-ability
is quite important for MPM event's correctness anyway so simplify code around
pollset creation so as not to suggest that APR_POLLSET_NODEFAULT if favored
against APR_POLLSET_WAKEABLE.

While at it account for the wakeup pipe in the pollset_size since not all
pollset methods seem to do it internally in APR.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1916925 13f79535-47bb-0310-9956-ffa450edef68