Merge r1724857 from trunk:

 
  *) mod_proxy_fcgi: Suppress HTTP error 503 and message 01075, 
     "Error dispatching request", when the cause appears to be 
     the client closing the connection. 

PR58118.  

Submitted By: Tobias Adolph <adolph lrz.de>
Committed By: covener


Submitted by: covener
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1726019 13f79535-47bb-0310-9956-ffa450edef68