### 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_
global SERVICE_PORTS, CONFIG_ENV_VARS
    SERVICE_PORTS = service_ports or parse_service_ports()
    globs = globals()
    protocol = get_protocol()
    
    for key, value in six.iteritems(DEFAULT_SERVICE_PORTS):
        key_upper = key.upper().replace("-", "_")
        
        port_var_name = "PORT_%s" % key_upper
        port_number = service_port(key)
        globs[port_var_name] = port_number
        url = "%s://%s:%s" % (protocol, LOCALSTACK_HOSTNAME, port_number)
        
        url_key = "TEST_%s_URL" % key_upper
        
        existing = os.environ.get(url_key)
        url = existing or url
        
        globs[url_key] = url
        
        os.environ[url_key] = url
    
    os.environ["LOCALSTACK_HOSTNAME"] = LOCALSTACK_HOSTNAME
    
    CONFIG_ENV_VARS += [
        "LOCALSTACK_" + v for v in CONFIG_ENV_VARS if not v.startswith("LOCALSTACK_")
    ]
    CONFIG_ENV_VARS = list(set(CONFIG_ENV_VARS))
def service_port(service_key):