MAHOUT-1341: Skip work directory initialization for clean task

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1525766 13f79535-47bb-0310-9956-ffa450edef68
MAHOUT-1340 fix two tests to work with Hadoop 2 as well

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1525865 13f79535-47bb-0310-9956-ffa450edef68