Test suite for `serverroles` backend
    
    Tests retrieving roles/attributes and setting server attributes in various
    scenarios.
    
    https://fedorahosted.org/freeipa/ticket/5181
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Pavel Vomacka <pvomacka@redhat.com>