HIVE-5065 (part 3): Create proper (i.e.: non .q file based) junit tests for DagUtils and TezTask (Gunther Hagleitner)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/tez@1551819 13f79535-47bb-0310-9956-ffa450edef68