Merge "releasetools: Support generating downgrade A/B OTAs." into nyc-dev am: 5a4508bcef am: e7847765a6 am: a7dcbfb2d8 am: 712bf7d750 am: 6ea73e3566 am: 58bb2216da
am: c9ed71221b  -s ours

Change-Id: Iec2a92bfa77c8a76afa2474a61dae9382ac250a4