### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

* Create any table with any records
* Do a TransactGetItems on the table
* Localstack returns 
```
ResourceNotFoundException: Cannot do operations on a non-existent table
```

### Expected Behavior

TransactGetItems should succeed.

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

```
docker-compose up
```

`docker-compose.yml`
```
version: '3'

services:
  localstack:
    image: localstack/localstack
    environment:
      - DEFAULT_REGION=eu-west-2
      - SERVICES=dynamodb
      - DOCKER_HOST=unix:///var/run/docker.sock
    ports:
      - 4566:4566
```

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

```
#! /bin/bash
aws --endpoint-url=http://localhost:4566 dynamodb create-table --attribute-definitions AttributeName=forumId,AttributeType=S --table-name forum --key-schema AttributeName=forumId,KeyType=HASH --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5 > /dev/null
aws --endpoint-url=http://localhost:4566 dynamodb put-item --table-name forum --item '{"forumId": {"S": "forum001"}, "data": {"S": "helloworld"}}' > /dev/null
aws --endpoint-url=http://localhost:4566 dynamodb get-item --table-name forum --key '{"forumId": {"S": "forum001"}}' > /dev/null
# This one fails
aws --endpoint-url=http://localhost:4566 dynamodb transact-get-items --transact-items '[{"Get": {"Key":{"forumId": {"S": "forum001"}}, "TableName": "forum"}}]' > /dev/null
```


### Environment

```markdown
- OS: MacOS 10.15.7
- LocalStack: latest, digest 843db39ff1df83fd537e15b30e39d6fb8c3590efd6bf3f6f96b1734418fbd19f
```


### Anything else?

This works in `localstack/localstack:0.14.1`
latest_stream_arn = table.latest_stream_arn
        testutil.create_lambda_function(
            handler_file=TEST_LAMBDA_PYTHON_ECHO,
            func_name=function_name,
            runtime=LAMBDA_RUNTIME_PYTHON36,
        )
        lambda_client = aws_stack.create_external_boto_client("lambda")
        lambda_client.create_event_source_mapping(
            EventSourceArn=latest_stream_arn, FunctionName=function_name
        )
        item = {"SK": short_uid(), "Name": "name-{}".format(short_uid())}
        table.put_item(Item=item)
        events = retry(
            check_expected_lambda_log_events_length,
            retries=3,
            sleep=1,
            function_name=function_name,
            expected_length=1,
            regex_filter=r"Records",
        )
        assert len(events) == 1
        assert len(events[0]["Records"]) == 1
        dynamodb_event = events[0]["Records"][0]["dynamodb"]
        assert dynamodb_event["StreamViewType"] == "NEW_AND_OLD_IMAGES"
        assert dynamodb_event["Keys"] == {"SK": {"S": item["SK"]}}
        assert dynamodb_event["NewImage"]["Name"] == {"S": item["Name"]}
        assert "SequenceNumber" in dynamodb_event
        dynamodb = aws_stack.create_external_boto_client("dynamodb")
        dynamodb.delete_table(TableName=table_name)
    def test_dynamodb_batch_write_item(self):