core: Disallow multiple Listen on the same IP:port when listener buckets

are configured (ListenCoresBucketsRatio > 0), consistently with the single
bucket case (default), thus fixing the leak of the corresponding socket
descriptors on graceful restart.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1789220 13f79535-47bb-0310-9956-ffa450edef68