Replacing dup() with fcntl F_DUPFD_CLOEXEC creates the duplicate
file descriptor with CLOEXEC so it won't be leaked to child
processes if the process fork()s later.
Signed-off-by: Derek Foreman <derekf@osg.samsung.com> Reviewed-by: Kristian Høgsberg <krh@bitplanet.net> Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>