Clear up authorization state docs

- Indicates which int values can be sent via the
EXTRA_CLIENT_AUTHORIZATION_STATE extra

- Explicitly mentions how much time clients have to clean up their state
with a nanoapp so there's no ambiguity.

Fixes: 181350428
Test: presubmits
Change-Id: Id39c233b8678450e3c7687ed2bcb1c1f4516f8d7