HDFS-5285. Flatten INodeFile hierarchy: Replace INodeFileUnderConstruction and INodeFileUnderConstructionWithSnapshot with FileUnderContructionFeature.  Contributed by jing9


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1544389 13f79535-47bb-0310-9956-ffa450edef68