worker MPM:

Don't create a listener thread until we have a worker thread.  Otherwise,
in situations where we'll have to wait a while to take over scoreboard
slots from a previous generation, we'll be accepting connections we can't
process yet.

Don't let the listener thread clobber the scoreboard entry of the first
worker thread.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@94420 13f79535-47bb-0310-9956-ffa450edef68