HBASE-10143 replace WritableFactories's hashmap with ConcurrentHashMap (Liang Xie via Stack)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1559924 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10110. hadoop-auth has a build break due to missing dependency. Contributed by Chuan Liu

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1559927 13f79535-47bb-0310-9956-ffa450edef68