use exact path to clustering results instead of wild-card

Detail is available at https://issues.apache.org/jira/browse/MAHOUT-1593

Briefly speaking, kmeans-clustering example script doesn't run correctly with Hadoop version: 2.4.0.2.1.1.0-385. The reason is that the script uses wild-carded path for clustering result directory, which is not returning the correct path. I replaced the wild-carded path with a simple combination of commands that returns the exact path.