MAHOUT-1291 fix for: MahoutDriver yields cosmetically suboptimal exception when bin/mahout runs without args, on some Hadoop versions

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1507398 13f79535-47bb-0310-9956-ffa450edef68
MAHOUT-1291: MahoutDriver yields cosmetically suboptimal exception when bin/mahout runs without args, on some Hadoop versions

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1507404 13f79535-47bb-0310-9956-ffa450edef68