test(Client): fix client test for guzzle5 promises
test(Client): fix client test for guzzle5 promises

sphereio/commercetools-php-sdk,sphereio/commercetools-php-sdk,sphereio/sphere-php-sdk,sphereio/sphere-php-sdk,sphereio/commercetools-php-sdk,sphereio/sphere-php-sdk,sphereio/commercetools-php-sdk,sphereio/sphere-php-sdk