HADOOP-9672. Upgrade Avro dependency to 1.7.4. Contributed by Sandy Ryza.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1512314 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9789. Support server advertised kerberos principals (daryn)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1512380 13f79535-47bb-0310-9956-ffa450edef68