Removed some code from the mutex-protected block in ap_queue_pop().

Removed some code from the mutex-protected block in ap_queue_pop().
If the worker thread synchronization is working properly, it's not
necessary to set these fields to NULL after removing an element from
the queue, and it's IMO more important to have a shorter code path
leading up to the mutex_unlock.  I left in support for NULLing the
fields when debugging, though.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@94850 13f79535-47bb-0310-9956-ffa450edef68