HDFS-5840. Follow-up to HDFS-5138 to improve error handling during partial upgrade failures. Contributed by Aaron T. Myers, Suresh Srinivas, and Jing Zhao.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1581260 13f79535-47bb-0310-9956-ffa450edef68