PIG-3767: Work with TEZ-668 which allows starting and closing of inputs and outputs (rohini)

git-svn-id: https://svn.apache.org/repos/asf/pig/branches/tez@1569428 13f79535-47bb-0310-9956-ffa450edef68
PIG-3768: TezCompiler.visitUnion() doesn't add compiled TezOp to phyToTezOpMap (cheolsoo)


git-svn-id: https://svn.apache.org/repos/asf/pig/branches/tez@1569501 13f79535-47bb-0310-9956-ffa450edef68