### 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_
"BUCKET_MARKER_LOCAL",
    "SYNCHRONOUS_SNS_EVENTS",
    "SYNCHRONOUS_SQS_EVENTS",
    "SYNCHRONOUS_DYNAMODB_EVENTS",
    "DYNAMODB_HEAP_SIZE",
    "MAIN_CONTAINER_NAME",
    "LAMBDA_DOCKER_DNS",
    "PERSISTENCE_SINGLE_FILE",
    "S3_SKIP_SIGNATURE_VALIDATION",
    "DEVELOP",
    "DEVELOP_PORT",
    "WAIT_FOR_DEBUGGER",
    "KINESIS_INITIALIZE_STREAMS",
    "TF_COMPAT_MODE",
    "LAMBDA_DOCKER_FLAGS",
    "LAMBDA_FORWARD_URL",
    "LAMBDA_CODE_EXTRACT_TIME",
    "THUNDRA_APIKEY",
    "THUNDRA_AGENT_JAVA_VERSION",
    "THUNDRA_AGENT_NODE_VERSION",
    "THUNDRA_AGENT_PYTHON_VERSION",
    "DISABLE_CORS_CHECKS",
    "DISABLE_CUSTOM_CORS_S3",
    "DISABLE_CUSTOM_CORS_APIGATEWAY",
    "EXTRA_CORS_ALLOWED_HEADERS",
    "EXTRA_CORS_EXPOSE_HEADERS",
    "EXTRA_CORS_ALLOWED_ORIGINS",
    "ENABLE_CONFIG_UPDATES",
    "LOCALSTACK_HTTP_PROXY",
    "LOCALSTACK_HTTPS_PROXY",