# Type of request: This is a bug report

# Detailed description
S3 list buckets returns a different format for CreationDate than the one expected by the Java SDK and parsing fails. Using Java SDK 2.13.39. Also verified w/ .40, .38, .30 and .20. Will check previous Docker releases for localstack.

``Unable to unmarshall response (Text '2020-06-17T15:26:46.032838+00:00' could not be parsed at index 19). Response Code: 200, Response Text: 
software.amazon.awssdk.core.exception.SdkClientException: Unable to unmarshall response (Text '2020-06-17T15:26:46.032838+00:00' could not be parsed at index 19). Response Code: 200, Response Text: <truncated...>
``

## Expected behavior
Return CreationDate in same format as the actual S3 API call.

## Actual behavior
Returns CreationDate in slightly different format from the actual S3 API call. Fractional seconds are included.

# Steps to reproduce
Run "aws s3api list-buckets" vs "aws s3api list-buckets --endpoint-url http://localstack:4566" and note different date format for CreationDate.

## Command used to start LocalStack
docker-compose:
```
  localstack:
    image: localstack/localstack
    ports:
      - '4566:4566'
    environment:
      SERVICES: s3
      DEBUG: 1
```
## Client code (AWS SDK code snippet, or sequence of "awslocal" commands)
See steps to reproduce.
response.headers['Content-Length'] = str(len(response._content))
                response.headers['Content-Type'] = 'application/xml; charset=utf-8'
                return response
        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 or key,
            
            
            bucket_name_in_host or key or (len(path[1:].split('/')) > 1 and len(path[1:].split('/')[1]) > 0),
            self.is_query_allowable(method, parsed.query)
        ])
        
        if should_send_notifications:
            
            if key:
                object_path = '/' + key
            elif bucket_name_in_host:
                object_path = parsed.path
            else:
                parts = parsed.path[1:].split('/', 1)
                object_path = parts[1] if parts[1][0] == '/' else '/%s' % parts[1]
            version_id = response.headers.get('x-amz-version-id', None)
            send_notifications(method, bucket_name, object_path, version_id)
        
        if method in ('PUT', 'DELETE') and ('/' not in path[1:] or len(path[1:].split('/')[1]) <= 0):
            event_type = (event_publisher.EVENT_S3_CREATE_BUCKET if method == 'PUT'
                else event_publisher.EVENT_S3_DELETE_BUCKET)
            event_publisher.fire_event(event_type, payload={'n': event_publisher.get_hash(bucket_name)})