Revert "IMPALA-1442: Ensure that Thrift transports are always buffered"

This reverts commit 34fa654ca0e6e8cf4c5cf5ddcc916b3b2b08f612.

Change-Id: I3aad41d0790810f1148f51ebaf5e107e84d9f409
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/5158
Reviewed-by: Ishaan Joshi <ishaan@cloudera.com>
Tested-by: Ishaan Joshi <ishaan@cloudera.com>