Review Request : MAPREDUCE-2149 : an improvement to DistCp setup.

[Raghu Angadi]

https://issues.apache.org/jira/browse/HADOOP-7023 : Distcp : setup with
update is too slow when latency is high

This improves 'distcp -update' across geographically separated clusters.
All the test pass and patch is tested in cluster.

Thanks,
Raghu.