adtrustinstance: Wait for sidgen task completion
    
    As part of hardening of adtrust installer, we should wait until
    the sidgen task is completed before continuing, as it can take
    considerable amount of time for a larger deployment.
    
    https://fedorahosted.org/freeipa/ticket/5134
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>