loader: allow booting from pool with log device

Apparently people are using log with boot pool, so we can not just
error out there. Still we will need to investigate how to handle
log properly.

stand/libsa/zfs/zfs.c

@@ -669,11 +669,14 @@ zfs_dev_open(struct open_file *f, ...)
 		spa = spa_find_by_guid(dev->pool_guid);
 	if (!spa)
 		return (ENXIO);
+#if 0
+	/* Apparently too many are using slog with boot pool. */
 	if (spa->spa_with_log) {
 		printf("Reading pool %s is not supported due to log device.\n",
 		    spa->spa_name);
 		return (ENXIO);
 	}
+#endif
 	mount = malloc(sizeof(*mount));
 	if (mount == NULL)
 		rv = ENOMEM;