Delay requesting chat messages after 412 and 404

[nickvergessen]

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Steps to reproduce

1. Disable brute force protection
2. Open a chat in one browser
3. In a second browser login and remove the session of browser 1

In a bigger scale this can happen for a full instance when switching the session handler:
https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/caching_configuration.html#using-the-redis-session-handler

Expected behaviour

Normal situation

Actual behaviour

Browser 1 sends the chat request multiple times per second. There should at least be a wait of 10 seconds or something. And after X failed attempts we should give up.