Merge r1306409:

* Add the forcerecovery balancer parameter that determines if recovery for
  balancer workers without considering the retry value of workers is enforced.
  There might be cases where an already overloaded backend can get into deeper
  trouble if the recovery of all workers is enforced without considering the
  retry parameter of each worker

Committed by: rpluem
Reviewed by: rpluem, covener, sf


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1307835 13f79535-47bb-0310-9956-ffa450edef68