### 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_
return platform.system() == "Linux"
def ping(host):
    """Returns True if host responds to a ping request"""
    is_windows = platform.system().lower() == "windows"
    ping_opts = "-n 1" if is_windows else "-c 1"
    args = "ping %s %s" % (ping_opts, host)
    return (
        subprocess.call(args, shell=not is_windows, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        == 0
    )
def in_docker():
    """
    Returns True if running in a docker container, else False
    Ref. https://docs.docker.com/config/containers/runmetrics/#control-groups
    """
    if OVERRIDE_IN_DOCKER:
        return True
    
    if os.path.exists("/.dockerenv"):
        return True
    if os.path.exists("/run/.containerenv"):
        return True
    if not os.path.exists("/proc/1/cgroup"):
        return False