NXDOMAIN errors should not be retried

The standard retryer keeps retrying domains that do not resolve. This
hangs the execution until retries are exhausted.
NXDOMAIN or 'no such host' errors are not transient and should fail immediately.
An example would be when a user enters an invalid region that doesn't resolve.

aws/retry/retryable_error.go

@@ -95,8 +95,13 @@ func (r RetryableConnectionError) IsErrorRetryable(err error) aws.Ternary {
 	var timeoutErr interface{ Timeout() bool }
 	var urlErr *url.Error
 	var netOpErr *net.OpError
+	var dnsError *net.DNSError
 
 	switch {
+	case errors.As(err, &dnsError):
+		// NXDOMAIN errors should not be retried
+		retryable = false
+
 	case errors.As(err, &conErr) && conErr.ConnectionError():
 		retryable = true