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

This reverts commit 17642fb3e40de4593f0a928cf0f8e3e482626b25.

Change-Id: I79771d1d22ce4b28b90e95a880375bf45d81cf0d
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/5157
Reviewed-by: Ishaan Joshi <ishaan@cloudera.com>
Tested-by: Ishaan Joshi <ishaan@cloudera.com>