# 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.
from localstack.utils.analytics import event_publisher
from localstack.utils.http_utils import uses_chunked_encoding
from localstack.utils.persistence import PersistingProxyListener
from localstack.utils.aws.aws_responses import requests_response
CONTENT_SHA256_HEADER = 'x-amz-content-sha256'
STREAMING_HMAC_PAYLOAD = 'STREAMING-AWS4-HMAC-SHA256-PAYLOAD'
PORT_S3_BACKEND = None
S3_NOTIFICATIONS = {}
BUCKET_CORS = {}
BUCKET_LIFECYCLE = {}
BUCKET_REPLICATIONS = {}
BUCKET_ENCRYPTIONS = {}
OBJECT_LOCK_CONFIGS = {}
OBJECT_EXPIRY = {}
LOGGER = logging.getLogger(__name__)
XMLNS_S3 = 'http://s3.amazonaws.com/doc/2006-03-01/'
BUCKET_NAME_REGEX = (r'(?=^.{3,63}$)(?!^(\d+\.)+\d+$)' +
    r'(^(([a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])\.)*([a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])$)')
NOTIFICATION_DESTINATION_TYPES = ('Queue', 'Topic', 'CloudFunction', 'LambdaFunction')
OBJECT_METADATA_KEY_PREFIX = 'x-amz-meta-'
ALLOWED_HEADER_OVERRIDES = {
    'response-content-type': 'Content-Type',
    'response-content-language': 'Content-Language',
    'response-expires': 'Expires',
    'response-cache-control': 'Cache-Control',
    'response-content-disposition': 'Content-Disposition',
    'response-content-encoding': 'Content-Encoding',
}
POLICY_EXPIRATION_FORMAT = '%Y-%m-%dT%H:%M:%SZ'
def event_type_matches(events, action, api_method):