YARN-1570. Fixed formatting of the lines in YarnCommands.apt.vm docs source. Contributed by Akira Ajisaka.
svn merge --ignore-ancestry -c 1579797 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1579798 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6038. Merge r1579813 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1579814 13f79535-47bb-0310-9956-ffa450edef68
YARN-1855. Made Application-history server to be optional in MiniYARNCluster and thus avoid the failure of TestRMFailover#testRMWebAppRedirect. Contributed by Zhijie Shen.
svn merge --ignore-ancestry -c 1579838 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1579839 13f79535-47bb-0310-9956-ffa450edef68
YARN-1859. Fixed WebAppProxyServlet to correctly handle applications absent on the ResourceManager. Contributed by Zhijie Shen.
svn merge --ignore-ancestry -c 1579866 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1579867 13f79535-47bb-0310-9956-ffa450edef68