Changing server address breaks current session, requires restart

[VMelnalksnis]

Describe the bug Changing the server address after logging in has no effect, and requires a restart to apply.

To Reproduce Steps to reproduce the behavior:

1. Open Gnomeshade, log in
2. Go to 'Settings' and update the server address
3. Log out
4. Try to log in to the new server
5. See that requests are sent to the old server

Expected behavior Either configuration changes are applied, or the user is notified that a restart is required.

[VMelnalksnis]

The naive approach of just updating HttpClient.BaseAddress on configuration change does not work, because it cannot be updated after a request is sent.