Reset state in WriteBuffer when performing zero copy
Reset state in WriteBuffer when performing zero copy

Summary: Reset zero copy state in WriteBuffer when performing zero copy

Reviewed By: andreazevedo

Differential Revision: D14264356

fbshipit-source-id: 04c40ee97c790c41c8ba80d249c0fb35c9f01f6c

facebook/mcrouter,facebook/mcrouter,facebook/mcrouter,facebook/mcrouter