When a subscription is created using cloudformation:
```
"ProfileChangedSubscription": {
      "Type": "AWS::SNS::Subscription",
      "Properties": {
        "Endpoint": {
          "Fn::GetAtt": [
            "ProfileChangedQueue",
            "Arn"
          ]
        },
        "Protocol": "sqs",
        "FilterPolicy": {
          "eventType": [
            "created"
          ]
        },
        "TopicArn": {
          "Fn::ImportValue": {
            "Fn::Sub": "${ProfilesProfilePublishStack}-ProfileChangedTopic"
          }
        }
      }
    }
```

The specified subscription filter policy is not created. When I run `get-subscription-attributes`, I get information about non-existing filter policy:

```
{
    "Attributes": {
        "TopicArn": "arn:aws:sns:us-east-1:000000000000:profile-changed-topic",
        "Endpoint": "arn:aws:sqs:us-east-1:000000000000:profile-changed-queue",
        "Protocol": "sqs",
        "SubscriptionArn": "arn:aws:sns:us-east-1:000000000000:profile-changed-topic:936a58be-525b-4228-bfdb-c4b2f6048e8c",
        "FilterPolicy": "None"
    }
}
```
import re
import os
import json
import yaml
import base64
import logging
import traceback
import moto.cloudformation.utils
from six import iteritems
from six import string_types
from localstack.utils import common
from localstack.utils.aws import aws_stack
from localstack.utils.testutil import create_zip_file
from localstack.services.awslambda.lambda_api import get_handler_file_from_name
ACTION_CREATE = 'create'
ACTION_DELETE = 'delete'
PLACEHOLDER_RESOURCE_NAME = '__resource_name__'
LOG = logging.getLogger(__name__)
UPDATEABLE_RESOURCES = ['Lambda::Function', 'ApiGateway::Method']
NoDatesSafeLoader = yaml.SafeLoader
NoDatesSafeLoader.yaml_implicit_resolvers = {
    k: [r for r in v if r[0] != 'tag:yaml.org,2002:timestamp'] for
    k, v in NoDatesSafeLoader.yaml_implicit_resolvers.items()
}
def str_or_none(o):