users: Improve logged-in check when deleting users

When deleting a user account, we try to check if the user is
still logged in, but we are using an accountsservice API that
ignores console logins. But deleting a user that is logged
in on the console is just as bad, so use
act_user_is_logged_in_anywhere instead, which includes console
logins.

https://bugzilla.gnome.org/show_bug.cgi?id=721951