event, worker: initialize the objects used by signal_threads() first.

event, worker: initialize the objects used by signal_threads() first.

Follow up to r1835845.

If a signal is received early when the MPM children start, signal_threads() may
be called concurrently with start_streads() thus before the latter (or its
underlying threads like the listener_thread) had a chance to create and init
the queues, mutexes, pollset and sockets array used by the former.

So move those initializations to a new setup_threads_runtime() function called
before start_threads(), where the pruntime pool is also created.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1837354 13f79535-47bb-0310-9956-ffa450edef68