don't create new test ids unnecessarily
don't create new test ids unnecessarily

Summary: When deriving reasons from other reasons, always reuse their test id. One less variation.

Reviewed By: panagosg7

Differential Revision: D17076490

fbshipit-source-id: 80e6334fd357f7ff5fbf31782ec3c3254b12ee0c

samwgoldman/flow,gabelevi/flow,facebook/flow,mroch/flow,samwgoldman/flow,facebook/flow,gabelevi/flow,samwgoldman/flow,mroch/flow,facebook/flow,gabelevi/flow,facebook/flow,samwgoldman/flow,mroch/flow,mroch/flow,gabelevi/flow,gabelevi/flow,samwgoldman/flow,samwgoldman/flow,mroch/flow,mroch/flow,gabelevi/flow,samwgoldman/flow,facebook/flow,facebook/flow,facebook/flow,mroch/flow,gabelevi/flow