Increase the lead time such that any operations faster than 1000/s gets JITed, (default threshold in Open JDK is 15000). Ignore the cluster benchmarks behind a flag as they are not really micro benchmarks (robinanil)

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1477397 13f79535-47bb-0310-9956-ffa450edef68