keep.failed.task.files=true causes job failure on secure clusters

To support IsolationRunner, split info is written to local directories. This occurs inside MapTask#localizeConfiguration, which is called both tasktracker and by the child JVM. On a secure cluster, the tasktacker's attempt to write it fails, because the tasktracker does not have permission to write to the user's directory. It is likely that the call to localizeConfiguration in the tasktracker can be removed.