HDFS-6858. Allow dfs.data.transfer.saslproperties.resolver.class default to hadoop.security.saslproperties.resolver.class. Contributed by Benoy Antony.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1619256 13f79535-47bb-0310-9956-ffa450edef68