Re-add IDP ID upong logot

[blizzz]

    The logout method would clear the session which generates a new session id, so this should lead to a new cookie, so from my perspective clearing and setting afterwards should work fine.

https://github.com/nextcloud/server/blob/9e1d4312555ddc1009450b1f6b7078ae35790593/lib/private/Session/Internal.php#L109-L111

Originally posted by @juliushaertl in #683 (comment)