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!
if method == 'GET':
                return get_encryption(bucket)
        if modified_data is not None:
            return Request(data=modified_data, headers=headers, method=method)
        return True
    def return_response(self, method, path, data, headers, response):
        path = to_str(path)
        method = to_str(method)
        bucket_name = get_bucket_name(path, headers)
        
        hostname_parts = headers['host'].split('.')
        if (not bucket_name or len(bucket_name) == 0) and len(hostname_parts) > 1:
            bucket_name = hostname_parts[0]
        
        
        key = None
        if method == 'POST':
            key, redirect_url = multipart_content.find_multipart_redirect_url(data, headers)
            if key and redirect_url:
                response.status_code = 303
                response.headers['Location'] = expand_redirect_url(redirect_url, key, bucket_name)
                LOGGER.debug('S3 POST {} to {}'.format(response.status_code, response.headers['Location']))
        parsed = urlparse.urlparse(path)
        bucket_name_in_host = headers['host'].startswith(bucket_name)
        should_send_notifications = all([
            method in ('PUT', 'POST', 'DELETE'),
            '/' in path[1:] or bucket_name_in_host,
            
            
            bucket_name_in_host or (len(path[1:].split('/')) > 1 and len(path[1:].split('/')[1]) > 0),