[NAN] Remove failure reason codes from API per API review

Not all codes are actionable. Will add back if/as needed.

(cherry-pick of commit 4b47c3f5)

Bug: 31470256
Test: unit tests & integration (sl4a) tests.
Change-Id: Ibfc9df4dbd3b569caf4ade1da9d2ef43d99269a8