adtrustinstance: fix ID range comparison
    
    The ID range comparison was comparing numbers to a string or possibly
    to `None` and was tailored in such a way that the check would always
    pass although it went directly against the definition of the absolute
    value of a substitution.
    
    https://pagure.io/freeipa/issue/7002
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>