### 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_
try:
        if any(
            [
                os.path.exists("/sys/fs/cgroup/memory/docker/"),
                any(
                    "docker-" in file_names
                    for file_names in os.listdir("/sys/fs/cgroup/memory/system.slice")
                ),
                os.path.exists("/sys/fs/cgroup/docker/"),
                any(
                    "docker-" in file_names
                    for file_names in os.listdir("/sys/fs/cgroup/system.slice/")
                ),
            ]
        ):
            return False
    except Exception:
        pass
    with open("/proc/1/cgroup", "rt") as ifh:
        content = ifh.read()
        if "docker" in content:
            return True
        os_hostname = socket.gethostname()
        if os_hostname and os_hostname in content:
            return True
    return False
OVERRIDE_IN_DOCKER = is_env_true("OVERRIDE_IN_DOCKER")
is_in_docker = in_docker()
is_in_linux = is_linux()
CONFIG_PROFILE = os.environ.get("CONFIG_PROFILE", "").strip()