Logout Does Not Clear Logged-in User From Transient

[fluxism]

The function sucuriscan_unset_online_user_on_logout hooks wp_logout in order to remove the logged-in user from the online_users transient.
https://github.com/Sucuri/sucuri-wordpress-plugin/blob/master/src/lastlogins-loggedin.php#L129

However that function searches for the user by:

$current_user = wp_get_current_user();
$user_id = $current_user->ID;

This always returns 0, as the wp_logout hook fires after setting user_id to 0.

Consequently, a user logout never succeeds in clearing the user from the list of online users.

A fix is to hook clear_auth_cookie instead of wp_logout.