function _handleSuccess(oData, oResponse) {
			if (oResponse) {
				sToken = that._getHeader("x-csrf-token", oResponse.headers);
				if (sToken) {
					that.oServiceData.securityToken = sToken;
					// For compatibility with applications, that are using getHeaders() to retrieve the current
					// CSRF token additionally keep it in the oHeaders object
					that.oHeaders["x-csrf-token"] = sToken;
				} else {
					// Disable token handling, if service does not return tokens
					that.resetSecurityToken();
					that.bTokenHandling = false;
				}
			}

			if (fnSuccess) {
				fnSuccess(oData, oResponse);
			}
		}
refresh XSRF token by performing a GET request against the service root URL.

@param {function} [fnSuccess] a callback function which is called when the data has
           					 been successfully retrieved.
@param {function} [fnError] a callback function which is called when the request failed. The handler can have the parameter: oError which contains
 additional error information.

@param {boolean} [bAsync=false] true for asynchronous requests.

@return {object} an object which has an <code>abort</code> function to abort the current request.

@public