Kinesis consumer validation incorrectly requires aws.region property

AwsClientBuilder says: Only one of Region or EndpointConfiguration may be set.

But KinesisUtil still thinks: The AWS region ('aws.region') must be set in the config.

This doesn't affect configuration based on region, but makes testing with Kinesalite impossible. The Flink code needs to match the new opinion in AWS SDK (probably changed with . recent update).