ulogd: close logfile description in the exit path of parent process

ulogd: close logfile description in the exit path of parent process

Joan Touzet reported that file descriptor 3 was not ever closed
in the exit path of the parent process:

open("ulogd.conf", O_RDONLY)            = 3

That corresponds to the the file descriptor that was used to
parse the configuration file was not closed.

This closes: http://bugzilla.netfilter.org/show_bug.cgi?id=793

Reported-by: Joan Touzet <joant@cloudant.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>