Returns true if the current AMP is the lowest AMP on the same node as the invoking AMP, otherwise returns false.
If this method is invoked from a table operator that is associated with a map, then lowestAMPOnNode() returns true if the current AMP is the lowest AMP on the same node within the specified map, otherwise it returns false.
This information is useful for a table UDF or table operator that allows only the lowest AMP vproc to participate.