<!-- Love localstack? Please consider supporting our collective:
👉  https://opencollective.com/localstack/donate -->

Having upgraded to the latest LocalStack version, I've noticed that Docker containers from Lambda executions are immediately removed when they terminate.

This was added in https://github.com/localstack/localstack/pull/1584

I can appreciate the need to clean up containers, however this feature of having them stay up is actually very useful for debugging things when they go wrong!

Would it be possible to have a flag so that when running LocalStack we can specify whether to remove containers on completion? Something like:

```
services:
  localstack:
    image: localstack/localstack:latest
    ports:
      - "4567-4593:4567-4593"
    environment:
      - SERVICES=serverless,ssm,stepfunctions
      - DOCKER_HOST=unix:///var/run/docker.sock
      - LAMBDA_EXECUTOR=docker
      - REMOVE_CONTAINERS_ON_LAMBDA_TERMINATE=true #(or false)
    volumes:
      - "${TMPDIR:-/tmp/localstack}:/tmp/localstack"
      - "/var/run/docker.sock:/var/run/docker.sock"
```

Thanks for the great work folks!
if 'text/html' in response.headers.get('Content-Type', '') \
                        and not response_content_str.lower().startswith('<!doctype html'):
                    response.headers['Content-Type'] = 'application/xml; charset=utf-8'
                reset_content_length = True
            
            if method == 'DELETE':
                reset_content_length = True
            if reset_content_length:
                response.headers['content-length'] = len(response._content)
    def _update_location(self, content, bucket_name):
        bucket_name = normalize_bucket_name(bucket_name)
        host = config.HOSTNAME_EXTERNAL
        if ':' not in host:
            host = '%s:%s' % (host, config.PORT_S3)
        return re.sub(r'<Location>\s*([a-zA-Z0-9\-]+)://[^/]+/([^<]+)\s*</Location>',
            r'<Location>%s://%s/%s/\2</Location>' % (get_service_protocol(), host, bucket_name),
            content, flags=re.MULTILINE)
    @staticmethod
    def is_query_allowable(method, query):
        
        if not query:
            return True
        
        contains_cred = 'X-Amz-Credential' in query and 'X-Amz-Signature' in query
        contains_key = 'AWSAccessKeyId' in query and 'Signature' in query
        if (method == 'POST' and query.startswith('uploadId')) or contains_cred or contains_key:
            return True
UPDATE_S3 = ProxyListenerS3()