[keyserver] don't display the QR code if keyserver is already logged in

Summary:
If the keyserver is logged in with the identity service, we don't need the keyserver owner to do QR code auth

Depends on D12213

Test Plan: confirmed that the QR code is not displayed if the mariadb metadata table has auth metadata

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12618