Fixed tests depending on the MountSpec testdata
Fixed tests depending on the MountSpec testdata

Summary:
Added file MountSpec back to testdata folder.

Some tests depends on this file to be present and are failing without it.

Reviewed By: colriot

Differential Revision: D17631483

fbshipit-source-id: 32854a73ac787c5c3108968ba6b5615e5958f37a

facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho