The layout version is -43 until 2.0.4-alpha, but HDFS-4908 changed layout
version to -45.
so if My test cluster is running hadoop-2.0.4-alpha(-43), which is upgraded
from hadoop-1.0.4, then I want to upgrade using trunk(-45), how to do?
It cannot upgrade under HA, so I can use hadoop-1.0.4 core-site and
hdfs-site, then "start-dfs.sh -upgrade", but standby NN cannot upgrade,
so how to upgrade standby NN under HA?