super1: remove fd leak when opening /dev/urandom

As reported in
   https://bugzilla.novell.com/show_bug.cgi?id=527722

I forgot to close the fd after reading the random number.

Signed-off-by: NeilBrown <neilb@suse.de>

super1.c

@@ -685,6 +685,8 @@ static int update_super1(struct supertype *st, struct mdinfo *info,
 			__u32 r[4] = {random(), random(), random(), random()};
 			memcpy(sb->device_uuid, r, 16);
 		}
+		if (rfd >= 0)
+			close(rfd);
 
 		sb->dev_roles[i] =
 			__cpu_to_le16(info->disk.raid_disk);