Rename setPathRootId to setPathObjectId
Rename setPathRootId to setPathObjectId

Summary: This diff renames ```SetPathRootId``` to ```SetPathObjectId``` as we want to support BLOB

Reviewed By: chadaustin

Differential Revision: D30404536

fbshipit-source-id: f34446ec20aeaf87f5f61e29e421a9bceb0b2a4a

nodakai/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman,nodakai/watchman