1. add comments for each data fail cause.
2. refactor dataFailCause from enum to int
Bug: 119891533
Test: Build & unit test
Change-Id: Ic453f80a3d0ccd22c6c4c1f4b2c90e2bf40cfbe1
(cherry picked from commit 3016167192)
Merged-in: Ic453f80a3d0ccd22c6c4c1f4b2c90e2bf40cfbe1