Hello all,

I have noticed that when I generate a presigned url for a file that will be uploaded to S3 that the Lambda function does not get triggered. It seems to only be happening for presigned url. I was able to successful have it trigger when I use the command line and upload a file through `aws s3 cp`. 

To recreate:
1: have any lambda function be added to an s3 bucket. My lambda configurations look as followed:
```
aws s3api --endpoint-url=http://localstack:4572 create-bucket --bucket mybucket;
aws s3api --endpoint-url=http://localstack:4572 create-bucket --bucket code;
aws s3 cp --endpoint-url=http://localstack:4572 --acl public-read /resources/example.zip s3://code/;
aws lambda create-function --endpoint-url=http://localstack:4574 --function-name MyLambdaFunction--runtime 'nodejs8.10' --handler 'index.handler' --role 'anyRole' --code S3Bucket=code,S3Key=example.zip,S3ObjectVersion=1.0.0;
```
Then add this lambda configuration to the bucket
```
{
    "LambdaFunctionConfigurations": [
        {
            "LambdaFunctionArn": "arn:aws:lambda:us-east-1:000000000000:function:MyLambdaFunction",
            "Events": [
                "s3:ObjectCreated:*"
            ]
        }
    ]
}
```
by running
```
aws s3api --endpoint-url=http://localstack:4572 put-bucket-notification-configuration --bucket 'mybucket' --notification-configuration file:///resources/notification.json;
```
2: Generate a presigned url for the bucket you added the lambda too

```
aws s3 presign --endpoint-url=http://localstack:4572 s3://mybucket/test.txt  --expires-in 300
```
3:
```
 curl --upload-file test.txt -v http://localstack:4572/mybucket/test.txt?AWSAccess
KeyId=dummyaccess&Expires=1571680684&Signature=TbCFh1rzkNYwNEooaQKcJPF4%2Fss%3D
```

Lambda does not seem to get triggered.

Any help or fixes?

Thank you so much for your time and help. Localstack has been a great tool!
"""Tests for the existence of the specified bucket. Returns the error code
    if the bucket does not exist (200 if the bucket does exist).
    """
    s3_client = aws_stack.connect_to_service('s3')
    try:
        s3_client.head_bucket(Bucket=bucket_name)
    except ClientError as err:
        error_code = err.response.get('Error').get('Code')
        return False, error_code
    return True, 200
def check_content_md5(data, headers):
    actual = md5(strip_chunk_signatures(data))
    expected = headers['Content-MD5']
    try:
        expected = to_str(codecs.encode(base64.b64decode(expected), 'hex'))
    except Exception:
        expected = '__invalid__'
    if actual != expected:
        result = {
            'Error': {
                'Code': 'InvalidDigest',
                'Message': 'The Content-MD5 you specified was invalid'
            }
        }
        content = xmltodict.unparse(result)
        return requests_response(content, status_code=400)
def expand_redirect_url(starting_url, key, bucket):