R1:8034b9d819eb

Don't require a device be registered in Almanac to do cluster init/resync steps

Summary:
Fixes T12893. See also PHI15. This is complicated but:

- In the documentation, we say "register your web devices with Almanac". We do this ourselves on `secure` and in the production Phacility cluster.
- We don't actually require you to do this, don't detect that you didn't, and there's no actual reason you need to.
- If you don't register your "web" devices, the only bad thing that really happens is that…