mod_status: Complete the data shown for async

MPMs in "auto" mode.  Added number of processes,
number of stopping processes and number
of busy and idle workers.

This changes only the key/value list of the
server-status "auto" output. The data is already
part of the "html" output.

Backport of r1837589 from trunk.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1839530 13f79535-47bb-0310-9956-ffa450edef68