Persistent conns in TSocketPool

Summary: Added support for persistent conns in TSocketPool
         Also, added some util functions in TNonblockingServer

Reviewed By: mcslee

Test Plan: Ran a test search cluster with these changes - open was only called once (I put fprintfs in open and close), after which the socket was reused

Revert: OK

TracCamp Project: Thrift

DiffCamp Revision: 11425


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665668 13f79535-47bb-0310-9956-ffa450edef68
3 files changed