Retry on 5xx HTTP error

nodejs sdk is currently retrying on 503 HTTP error only (https://github.com/commercetools/nodejs/blob/1167644b37db9af7baf511b8b14cdf6abf48f47c/packages/sdk-middleware-http/src/http.js#L215). According to the CTP documentation it should retry at least on 502 HTTP error (https://docs.commercetools.com/api/errors#502-bad-gateway). You may consider retrying also on other 5xx HTTP errors where it makes sense.