HADOOP-10079. log a warning message if group resolution takes too long (cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1538114 13f79535-47bb-0310-9956-ffa450edef68
Move HDFS-5035 to 2.2.1 in CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1538122 13f79535-47bb-0310-9956-ffa450edef68