tests: marking test_add_user_to_group as xfail to unexpected API response
tests: marking test_add_user_to_group as xfail to unexpected API response

Change-Id: I8e248f59ffe99176f779dcd80cb33fe0c87ff537

dwmarshall/pycontribs-jira,dwmarshall/pycontribs-jira,pycontribs/jira,pycontribs/jira