Merge r1294349 from trunk:

Prevent listener thread from ever updating a worker's scoreboard slot
    
The worker may be doing something else by now. This should take
care of slots staying in "L" state in the scoreboard

Submitted by: sf
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1364611 13f79535-47bb-0310-9956-ffa450edef68