Buffered tuple stream fixes.

Change-Id: I62cbe304c9fd9b5909ccf4bc9e91db37d3ef09a1
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3900
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3940