private static <TNode extends AvlNode> void fixHeight(TNode node) {
      final int heightLeft = height(node.avlLeft);
      final int heightRight = height(node.avlRight);
      node.avlHeight = 1 + Math.max(heightLeft, heightRight);
    }
Visit each node of the tree
@param root    the current root of the tree
@param visitor the AvlNodeVisitor instance
hbase-common/src/main/java/org/apache/hadoop/hbase/util/AvlUtil.java