### 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_
self._provider_config[service] = provider
    def bulk_set_provider_if_not_exists(self, services: List[str], provider: str):
        for service in services:
            self.set_provider_if_not_exists(service, provider)
    def __getitem__(self, item):
        return self.get_provider(item)
    def __setitem__(self, key, value):
        self.set_provider(key, value)
    def __len__(self):
        return len(self._provider_config)
    def __iter__(self):
        return self._provider_config.__iter__()
SERVICE_PROVIDER_CONFIG = ServiceProviderConfig("default")
for key, value in os.environ.items():
    if key.startswith("PROVIDER_OVERRIDE_"):
        SERVICE_PROVIDER_CONFIG.set_provider(key.lstrip("PROVIDER_OVERRIDE_").lower(), value)
if is_in_docker:
    dirs = Directories.for_container()
else:
    dirs = Directories.from_config()
dirs.mkdirs()
for path in [dirs.config, os.path.join(dirs.tmp, ".localstack")]:
    if path and os.path.isfile(path):
        print(
            f"warning: the config file .localstack is deprecated and no longer used, "
            f"please remove it by running rm {path}"
        )