[Integrator] - Web Service library return error when web service SSL is not validated

cURL verbose output: {"code":0,"message":"Return value of FusionDirectory\Rest\WebServiceCall::getAccessToken() must be of the type string, array returned","file":"/usr/share/php/FusionDirectory/FusionDirectory/Rest/WebServiceCall.php","line":116}

This is returned when trying to access the webservice in https instead of http.

The error message should be more precise than an PHP error.