loader: allow loader to accept zfs feature com.delphix:bookmark_written

We do not need to actually read bookmarks, just whitelist this feature.

Reported by:	mjg

stand/libsa/zfs/zfsimpl.c

@@ -134,6 +134,7 @@ static const char *features_for_read[] = {
 	"com.delphix:obsolete_counts",
 	"com.intel:allocation_classes",
 	"org.freebsd:zstd_compress",
+	"com.delphix:bookmark_written",
 	NULL
 };