suexec: Allow to log an error if exec fails by setting FD_CLOEXEC

on the log file instead of closing it.

PR: 10744
Submitted by: Nicolas Rachinsky
Reviewed by: Stefan Fritsch


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@821321 13f79535-47bb-0310-9956-ffa450edef68