iptables: fix printing of line numbers with --line-numbers arg

Commit bb34082d ("iptables --list chain rulenum") broke the line
numbering, starting with printing an offset of 2.

Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/iptables.c b/iptables.c
index cff8cf4..bf3cbca 100644
--- a/iptables.c
+++ b/iptables.c
@@ -737,7 +737,7 @@
 	flags = fw->ip.flags;
 
 	if (format & FMT_LINENUMBERS)
-		printf(FMT("%-4u ", "%u "), num+1);
+		printf(FMT("%-4u ", "%u "), num);
 
 	if (!(format & FMT_NOCOUNTS)) {
 		print_num(fw->counters.pcnt, format);