[native] Wait for authoritative keyserver login before setting avatar in registration flow

Summary:
When this logic was first built, currentUserInfo would appear after the authoritative keyserver auth occurred.

Now it appears after identity auth, so it's no longer the right thing to check here. Instead, we should check isLoggedInToKeyserver(authoritativeKeyserverID).

Test Plan: Make sure that I can register an account with a custom avatar, and that when the account is created the custom avatar appears

Reviewers: inka, tomek, marcin

Reviewed By: marcin

Differential Revision: https://phab.comm.dev/D11693