netfilter: add -n to iptables and ip6tables calls

To preload netfilter modules, criu runs "iptables -L" and "ip6tables -L"
before starting to dump or restore a process tree.

On systems with many entries, the above commands without the -n option
take a long time because of lengthy DNS lookups.
Signed-off-by: Saied Kazemi <saied@google.com>
Acked-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/netfilter.c

@@ -39,9 +39,9 @@ void preload_netfilter_modules(void)
 		pr_perror("failed to open /dev/null, using log fd for net module preload");
 	}
 	cr_system(fd, fd, fd, iptable_cmd_ipv4,
-		(char *[]) { iptable_cmd_ipv4, "-L", NULL}, 0);
+		(char *[]) { iptable_cmd_ipv4, "-L", "-n", NULL}, 0);
 	cr_system(fd, fd, fd, iptable_cmd_ipv6,
-		(char *[]) { iptable_cmd_ipv6, "-L", NULL}, 0);
+		(char *[]) { iptable_cmd_ipv6, "-L", "-n", NULL}, 0);
 	close_safe(&fd);
 }