### 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`
self,
        request_items,
        existing_items,
        unprocessed_put_items: List,
        unprocessed_delete_items: List,
    ):
        records = []
        record = self.get_record_template()
        unprocessed_items = {"PutRequest": {}, "DeleteRequest": {}}
        i = 0
        for table_name in sorted(request_items.keys()):
            
            stream_spec = dynamodb_get_table_stream_specification(table_name=table_name)
            if stream_spec:
                record["dynamodb"]["StreamViewType"] = stream_spec["StreamViewType"]
            for request in request_items[table_name]:
                put_request = request.get("PutRequest")
                if put_request:
                    if existing_items and len(existing_items) > i:
                        existing_item = existing_items[i]
                        keys = SchemaExtractor.extract_keys(
                            item=put_request["Item"], table_name=table_name
                        )
                        new_record = copy.deepcopy(record)
                        new_record["eventID"] = short_uid()
                        new_record["dynamodb"]["SizeBytes"] = len(json.dumps(put_request["Item"]))
                        new_record["eventName"] = "INSERT" if not existing_item else "MODIFY"
                        new_record["dynamodb"]["Keys"] = keys
                        new_record["dynamodb"]["NewImage"] = put_request["Item"]
                        if existing_item: