image-desc: Use unsigned format for autofs

Both the kernel and criu uses unsigned int
for it, make the format appropriate.

	| struct mount_info {
	|	...
	|	unsigned int		s_dev;
	|	...
	| }

We didn't see negative number here in real life so
I don't think if such %d to %u convention cause
backward compatibility problem ever.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/image-desc.c

@@ -78,7 +78,7 @@ struct cr_fd_desc_tmpl imgset_template[CR_FD_MAX] = {
 	FD_ENTRY_F(IP6TABLES,	"ip6tables-%d", O_NOBUF),
 	FD_ENTRY_F(TMPFS_IMG,	"tmpfs-%d.tar.gz", O_NOBUF),
 	FD_ENTRY_F(TMPFS_DEV,	"tmpfs-dev-%d.tar.gz", O_NOBUF),
-	FD_ENTRY_F(AUTOFS,	"autofs-%d", O_NOBUF),
+	FD_ENTRY_F(AUTOFS,	"autofs-%u", O_NOBUF),
 	FD_ENTRY(BINFMT_MISC_OLD, "binfmt-misc-%d"),
 	FD_ENTRY(BINFMT_MISC,	"binfmt-misc"),
 	FD_ENTRY(TTY_FILES,	"tty"),