Tweak worker thread accounting routines to eliminate

server hang when number of Listen directives in httpd.conf
is greater than or equal to the setting of ThreadsPerChild.
Reviewed by:	 stoddard, trawick, geoff


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@103127 13f79535-47bb-0310-9956-ffa450edef68