[lib] Include KeyserverAuthResult payload for KEYSERVER_AUTH_SUCCESS

Summary: Based on types in lib/types/redux-types.js, it should not be possible to dispatch KEYSERVER_AUTH_SUCCESS with payload being undefined. Not sure if this was intentionally left out... if so, should we consider updating the types to match?

Test Plan: Flow

Reviewers: tomek, inka

Reviewed By: tomek

Differential Revision: https://phab.comm.dev/D11054