Tests: Add missing attributes to test_xmlrpc/test_trust tests
    
    Several tests in test_xmlrpc/test_trust_plugin.py fail because some attributes
    are not expected. Fixing the tests so that the extra attributes are recognized.
    
    https://fedorahosted.org/freeipa/ticket/6276
    
    Reviewed-By: Ganna Kaihorodova <gkaihoro@redhat.com>