ignore message type that we don't want

[shawn-cx-li]

When setup SQS events in S3 bucket, a testing event will be pushed into queue, this PR is to ignore the unwanted messages

The test event body:

{
  Service: 'Amazon S3',
  Event: 's3:TestEvent',
  Time: '2020-09-15T01:38:05.620Z',
  Bucket: 'le-chris-nguyen-dev',
  RequestId: '6995D9A7AD11B7F6',
  HostId: 'rofW5HVDvoyVhbo4CZHGz23qtOF9hXFoeqDDgXm3VqccJ5s0RuGuYcHl9wFV6bZ0cDzoy9CTiBw='
}