api: add_user_to_group can now return False on failures
api: add_user_to_group can now return False on failures

Change-Id: I6925244afa80506a77be77f7000f53c3b37746f6

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