Back out "Improve IOBuf::create smart-combine behavior"
Back out "Improve IOBuf::create smart-combine behavior"

Summary:
Original commit: rFBS47a319bded0a3d56e06b6e85205138e942a6a3bc
Original diff: D37759017 (https://github.com/facebook/folly/commit/1ccd0e707f947a6683d826ee99b7619e948162a3)

Reviewed By: Prowindy

Differential Revision: D37890008

fbshipit-source-id: 6573aaa06a3fea639e7d3dbd0050e9357bccd49e

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly