Use the proxy_runtime_stat that either comes from scoreboard or

directly allocating memory if there is no scoreboard support or it is not
neaded, due to the fact that we have single child process.

Submitted by: mturk


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@104618 13f79535-47bb-0310-9956-ffa450edef68