Merge r1207926 from trunk:

Logic which makes the balancer "active" or not... so we can turn them
off and on as needed.
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1207927 13f79535-47bb-0310-9956-ffa450edef68