Reverted the essertion for replica uninstall returncode
    
    As the issue with ipa installer always returning 0 returncode was addressed,
    the test needs to be made aware of this change.
    
    https://fedorahosted.org/freeipa/ticket/6401
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>