# 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.
for key, value in query_map.items():
        if key.lower().startswith(OBJECT_METADATA_KEY_PREFIX):
            if headers.get(key) is None:
                headers[key] = value[0]
def fix_location_constraint(response):
    """ Make sure we return a valid non-empty LocationConstraint, as this otherwise breaks Serverless. """
    try:
        content = to_str(response.content or '') or ''
    except Exception:
        content = ''
    if 'LocationConstraint' in content:
        pattern = r'<LocationConstraint([^>]*)>\s*</LocationConstraint>'
        replace = r'<LocationConstraint\1>%s</LocationConstraint>' % aws_stack.get_region()
        response._content = re.sub(pattern, replace, content)
        remove_xml_preamble(response)
def fix_range_content_type(bucket_name, path, headers, response):
    
    if 'Range' not in headers:
        return
    s3_client = aws_stack.connect_to_service('s3')
    path = urlparse.unquote(path)
    key_name = get_key_name(path, headers)
    result = s3_client.head_object(Bucket=bucket_name, Key=key_name)
    content_type = result['ContentType']
    if response.headers.get('Content-Type') == 'text/html; charset=utf-8':
        response.headers['Content-Type'] = content_type
def fix_delete_objects_response(bucket_name, method, parsed_path, data, headers, response):