I'm trying to start localstack in a containerized Jenkins build agent for unit testing. In other words, trying to start the localstack docker container from within a docker container. We do this all the time with other images, using the method of mounting `/var/run/docker.sock` in the "parent" container, but localstack will not start.

I get this error:

```
2019-11-08T18:53:53:ERROR:localstack.services.generic_proxy: Exception running proxy on port 8081: [Errno 13] Permission denied: '/tmp/localstack/server.test.pem' Traceback (most recent call last):
  File "/opt/code/localstack/localstack/services/generic_proxy.py", line 384, in run_cmd
    combined_file, cert_file_name, key_file_name = GenericProxy.create_ssl_cert(serial_number=self.port)
  File "/opt/code/localstack/localstack/services/generic_proxy.py", line 401, in create_ssl_cert
    return generate_ssl_cert(SERVER_CERT_PEM_FILE, serial_number=serial_number)
  File "/opt/code/localstack/localstack/utils/common.py", line 828, in generate_ssl_cert
    save_file(target_file, file_content)
  File "/opt/code/localstack/localstack/utils/common.py", line 642, in save_file
    with open(file, mode) as f:
PermissionError: [Errno 13] Permission denied: '/tmp/localstack/server.test.pem'
```

Port 8081 is not already in use, and `/tmp/localstack` is writable, so I don't understand why it's getting permission denied.
'href': '%s/%s' % (base_path, i['responseType'])
            }
        }
        i['responseParameters'] = i.get('responseParameters', {})
        i['responseTemplates'] = i.get('responseTemplates', {})
        return i
    result = {
        '_links': {
            'curies': {
                'href': href,
                'name': 'gatewayresponse',
                'templated': True
            },
            'self': {'href': base_path},
            'first': {'href': base_path},
            'gatewayresponse:by-type': {
                'href': '%s/{response_type}' % base_path,
                'templated': True
            },
            'item': [{'href': '%s/%s' % (base_path, r['responseType'])} for r in result]
        },
        '_embedded': {
            'item': [item(i) for i in result]
        },
        
        
        'item': [item(i) for i in result]
    }
    return result
def put_gateway_response(api_id, response_type, data):