HDFS-4013. Merge r1455754 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1455756 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9399. protoc maven plugin doesn't work on mvn 3.0.2. Contributed by Todd Lipcon.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1455772 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-HADOOP-9078-branch-2-gd