Performance Patch: Disable Client-Side Nagle By Default

HADOOP-2232 was a valuable contribution, but I would suggest that Hadoop IPC should disable Nagle's algorithm by default, to improve performance system-wide. Nagle just adds delay to network connections, which is unnecessary in the high bandwidth networks that Hadoop uses. As it stands, this becomes an obscure, little known but important performance optimization (especially for HBase), which took us days to track down during a performance tuning exercise. Obviously integrating this optimization into the Hadoop release will require performance testing to validate that it doesn't harm performance, but it should only help.

I will submit a patch for how to address this in trunk.