### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When attempting to sign some document using Localstack KMS inside a lambda container (also running on localstack), the localstack KMS listener returns some unknown error.

The KMS key and lambda containers have been created from the same CDK app deploy, and I can see all the resources in the localstack web console.

The test application I'm using to prove this behaviour is available here:
https://github.com/LukaHedt/localstack_kms_test

Instructions to run are in the main Readme, and the `/localstack/Readme.md` file.

`aws-sdk` returns an unknown error, and the localstack docker logs that I receive are available here:
https://pastebin.com/58Z3fXi3

Have done an amount of testing and can confidently claim the following:
- Have tested on multiple machines with the same outcome
- Doesn’t make a difference if I specify an ARN or a KeyID in the signing request
- Downgrading localstack versions either didn’t make a difference, or I couldn’t actually deploy a localstack container with version 0.12.20 or lower.

### Expected Behavior

KMS Sign should return a signature for the given payload.

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

Test application demonstrating the current behaviour is available here:

https://github.com/LukaHedt/localstack_kms_test

Full instructions to run are in the `/localstack/Readme.md` file.


### Environment

```markdown
- OS: MacOS Monteray 12.3
- LocalStack: 0.14.0
```


### Anything else?

_No response_
table_name, streams_enabled_cache
            )
            if event_sources_or_streams_enabled:
                existing_items = self._thread_local("existing_item")
                records = get_updated_records(table_name, existing_items)
        elif action == "BatchWriteItem":
            records, unprocessed_items = self.prepare_batch_write_item_records(record, data)
            for record in records:
                event_sources_or_streams_enabled = (
                    event_sources_or_streams_enabled
                    or has_event_sources_or_streams_enabled(
                        record["eventSourceARN"], streams_enabled_cache
                    )
                )
            if response.status_code == 200 and any(unprocessed_items):
                content = json.loads(to_str(response.content))
                table_name = list(data["RequestItems"].keys())[0]
                if table_name not in content["UnprocessedItems"]:
                    content["UnprocessedItems"][table_name] = []
                for key in ["PutRequest", "DeleteRequest"]:
                    if any(unprocessed_items[key]):
                        content["UnprocessedItems"][table_name].append(
                            {key: unprocessed_items[key]}
                        )
                unprocessed = content["UnprocessedItems"]
                for key in list(unprocessed.keys()):
                    if not unprocessed.get(key):
                        del unprocessed[key]
                response._content = json.dumps(content)
                fix_headers_for_updated_response(response)