HDFS-2949. Add check to active state transition to prevent operator-induced split brain. Contributed by Rushabh S Shah.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1594709 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10401. ShellBasedUnixGroupsMapping#getGroups does not always return primary group first (ajisakaa via cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1594714 13f79535-47bb-0310-9956-ffa450edef68