svn merge -c 1452338 FIXES: HADOOP-9352. Expose UGI.setLoginUser for tests (daryn)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1452339 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1452384 FIXES: HDFS-4128. 2NN gets stuck in inconsistent state if edit log replay fails in the middle (kihwal via daryn)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1452388 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-YAHOO-258-branch-2-gd