# 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.
""" check whether the given object path matches all of the given filters """
    filters = filters or {}
    s3_filter = _get_s3_filter(filters)
    for rule in s3_filter.get('FilterRule', []):
        rule_name_lower = rule['Name'].lower()
        if rule_name_lower == 'prefix':
            if not prefix_with_slash(object_path).startswith(prefix_with_slash(rule['Value'])):
                return False
        elif rule_name_lower == 'suffix':
            if not object_path.endswith(rule['Value']):
                return False
        else:
            LOGGER.warning('Unknown filter name: "%s"' % rule['Name'])
    return True
def _get_s3_filter(filters):
    return filters.get('S3Key', filters.get('Key', {}))
def prefix_with_slash(s):
    return s if s[0] == '/' else '/%s' % s
def get_event_message(event_name, bucket_name, file_name='testfile.txt', version_id=None, file_size=0):
    
    bucket_name = normalize_bucket_name(bucket_name)
    return {
        'Records': [{
            'eventVersion': '2.0',
            'eventSource': 'aws:s3',
            'awsRegion': aws_stack.get_region(),
            'eventTime': timestamp_millis(),
            'eventName': event_name,
            'userIdentity': {