mod_proxy: Improve the balancer member data shown

in mod_status when "ProxyStatus" is "On":
add "busy" count and show byte counts in auto
mode always in units of kilobytes.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1837588 13f79535-47bb-0310-9956-ffa450edef68