get the last worker in a given child initialized properly

get the last worker in a given child initialized properly
by getting a new pool for its own proc_info structure instead
of overlaying the pool in the proc_info structure for the
prior thread

we also move through the SERVER_STARTING scoreboard state for this
worker, though this isn't as important as with the other workers,
for which a new thread must be created (potentially time consuming)

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@88280 13f79535-47bb-0310-9956-ffa450edef68