Set field status to UNDEFINED when a new builder instance is created
Set field status to UNDEFINED when a new builder instance is created

Summary: As title. No need to do this beforehand (when they have DEFAULT value).

Reviewed By: int3

Differential Revision: D4970481

fbshipit-source-id: 3cd03e716f089cdb672c1808a825b7ce6a6e1eae

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