Merge -c 1488806 from trunk to branch-2 to fix YARN-749. Rename ResourceRequest.(get,set)HostName to ResourceRequest.(get,set)ResourceName. Contributed by Arun C. Murthy.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1488807 13f79535-47bb-0310-9956-ffa450edef68