Add audit log events when disconnecting sessions during MFA re-auth

[wojcik91]

During MFA flow we check if there are any active sessions for a given device and location and close them before creating a new VPN session.
This can happen if a client fails and tries to reconnect before the session is cleared due to a timeout.
As of now there is no dedicated event for this logged in the activity log.

Result: Client with an active MFA-authorized connection restarts and reconnects quickly (before location-configured timeout). The connection is established and works as expected. In the DB we can check that the initial session is marked as disconnected.