dfs.namenode.redundancy.considerLoad is true by default and it is causing many test failures. Let's disable it in MiniDFSCluster.
Originally reported by weichiu: https://github.com/apache/hadoop/pull/2410#pullrequestreview-516144442
i've certain seen this option causing test failures in the past.
Maybe we should turn it off by default in MiniDDFSCluster, and only enable it for specific tests.