### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Starting localstack with the CLI `PROVIDER_OVERRIDE_SQS=asf bin/localstack --debug start` starts up correctly but then uses the `default` SQS provider.

### Expected Behavior

I would expect it to start the asf provider.

### How are you starting LocalStack?

With the `localstack` script

### Steps To Reproduce

* `PROVIDER_OVERRIDE_SQS=asf bin/localstack --debug start`
* `awslocal sqs create-queue --queue-name "test-queue"`

logs show:

```
2021-12-27T14:08:43.274:DEBUG:plugin.manager: instantiating plugin PluginSpec(localstack.aws.provider.sqs:default = <function sqs at 0x7f30e6d2b820>)
2021-12-27T14:08:43.274:DEBUG:plugin.manager: loading plugin localstack.aws.provider:sqs:default
2021-12-27T14:08:43.278:INFO:localstack.services.infra: Starting mock SQS service on http port 4566 ...
2021-12-27T14:08:43.279:INFO:localstack.services.infra: Starting mock SQS service on http port 4566 ...
2021-12-27T14:08:43.279:INFO:localstack.services.motoserver: starting moto server on http://0.0.0.0:38335
```

### Environment

```markdown
- OS: Ubuntu 20.04
- LocalStack: 13.2
```


### Anything else?

_No response_
"REQUESTS_CA_BUNDLE",
    "LEGACY_DOCKER_CLIENT",
    "EAGER_SERVICE_LOADING",
    "LAMBDA_STAY_OPEN_MODE",
]
for key, value in six.iteritems(DEFAULT_SERVICE_PORTS):
    clean_key = key.upper().replace("-", "_")
    CONFIG_ENV_VARS += [
        clean_key + "_BACKEND",
        clean_key + "_PORT",
        clean_key + "_PORT_EXTERNAL",
    ]
def collect_config_items() -> List[Tuple[str, Any]]:
    """Returns a list of key-value tuples of LocalStack configuration values."""
    none = object()  
    
    keys = []
    keys.extend(CONFIG_ENV_VARS)
    keys.append("DATA_DIR")
    keys.sort()
    values = globals()
    result = []
    for k in keys:
        v = values.get(k, none)
        if v is none:
            continue
        result.append((k, v))
    result.sort()
    return result
def ping(host):