Revert "Temporarily use blockimgdiff v2 for OTA."

This reverts commit d07bfc51.

Real fixes [1][2][3] are ready to merge. Time to revert the workaround.

[1] commit d47d8e14
[2] commit 1fc67631
[3] commit 937847ae

Bug: 22430577
Change-Id: Icd6623e8717c93ad1f12cd1ba43db5e006e928ad