[merge after release] enable IH sequence feature (#920)

* add logging to loader

* enable IH sequence feature

* clean

trie/flatdb_sub_trie_loader.go

@@ -888,8 +888,7 @@ func (c *IHCursor) Seek(seek []byte) ([]byte, []byte, bool, error) {
 		return k, v, false, nil
 	}
 
-	//return k, v, isSequence(seek, k), nil // will release sequence another time
-	return k, v, false, nil
+	return k, v, isSequence(seek, k), nil
 }
 
 /*