WifiEnterpriseConfiguration: Do not print credentials in toString

    public String toString() {

        StringBuffer sb = new StringBuffer();

        for (String key : mFields.keySet()) {

            sb.append(key).append(" ").append(mFields.get(key)).append("\n");

            // Don't display password in toString().

            String value = (key == PASSWORD_KEY) ? "<removed>" : mFields.get(key);

            sb.append(key).append(" ").append(value).append("\n");

        }

        return sb.toString();

    }