Tests for initHumanUsers and initinitRobotUsers.

Change the Cluster class in the process to implelement Teams API
calls and Oauth token fetches as interfaces, so that we can mock
them in the tests.

pkg/util/teams/teams.go

@@ -43,6 +43,10 @@ type httpClient interface {
 	Do(req *http.Request) (*http.Response, error)
 }
 
+type Interface interface {
+	TeamInfo(teamID, token string) (tm *Team, err error)
+}
+
 // API describes teams API
 type API struct {
 	httpClient