Sign in page post-email confirmation for new users shows unexpected server ID

[kittykat]

Steps to reproduce

1. Register an account with a username and password
2. Open email to verify email address and click on the link
3. When the confirmation loads, click ""Log in"" and look at the server on the page that loads

What happened?

Left is normal login page, right is when it's accessed through an email confirmation link:

Operating system

All

Browser information

All

URL for webapp

develop.element.io

Homeserver

matrix.org

Have you submitted a rageshake?

No

[t3chguy]

We can only fix this for the "happy path" without a spec change, where the happy path = the default server on that given Element instance. The 3PID verification flow gives us a hsUrl and an isUrl and there are no CS API endpoints which get a hsName from those.