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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!
for ip in candidates:
            if ping(ip):
                DOCKER_BRIDGE_IP = ip
                break
try:
    DOCKER_HOST_FROM_CONTAINER = DOCKER_BRIDGE_IP
    if not is_in_docker and not is_in_linux:
        
        
        if LOCALSTACK_HOSTNAME == HOSTNAME:
            DOCKER_HOST_FROM_CONTAINER = 'host.docker.internal'
    
    if is_in_docker and LOCALSTACK_HOSTNAME == DOCKER_BRIDGE_IP:
        DOCKER_HOST_FROM_CONTAINER = socket.gethostbyname('host.docker.internal')
        LOCALSTACK_HOSTNAME = DOCKER_HOST_FROM_CONTAINER
except socket.error:
    pass
if is_in_docker and not os.environ.get('LAMBDA_REMOTE_DOCKER', '').strip():
    LAMBDA_REMOTE_DOCKER = True
CONFIG_FILE_PATH = os.path.join(expanduser('~'), '.localstack')
no_proxy = ','.join(set((LOCALSTACK_HOSTNAME, HOSTNAME, LOCALHOST, '127.0.0.1', '[::1]')))
if os.environ.get('no_proxy'):
    os.environ['no_proxy'] += ',' + no_proxy
elif os.environ.get('NO_PROXY'):
    os.environ['NO_PROXY'] += ',' + no_proxy
else:
    os.environ['no_proxy'] = no_proxy
CLI_COMMANDS = {}
VALID_REGIONS = set(Session().get_available_regions('sns'))
def parse_service_ports():