merge from trunk r1299738:

mod_proxy_balancer: fix error message implying recovery during a markdown
(a fix for r962972)

Submitted by: covener
Reviewed by: jim, trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1301194 13f79535-47bb-0310-9956-ffa450edef68