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We have several Kinesis streams set up with event notifications that trigger lambdas.  When the LAMBDA_EXECUTOR is set to 'docker' and we send a large number or records to Kinesis, multiple Lambdas will execute, but currently they are failing to create with error:

```
Exception: Lambda process returned error status code: 1. Output:
time="2019-09-18T17:28:11Z" level=error msg="error getting events from daemon: net/http: request canceled" 
Error response from daemon: driver failed programming external connectivity on endpoint busy_sanderson (a78e45a41d0ce5b0d8bab6ff54344fc34fe2b4969f55bf568e753121abc8759e): Bind for 0.0.0.0:38763 failed: port is already allocated
```

I believe this is due to the new debug_java_port introduced with this PR https://github.com/localstack/localstack/pull/1523

With this change, you are setting the port in the constructor by using a method known to have a race condition (https://github.com/localstack/localstack/blob/master/localstack/utils/common.py#L354)
(https://gist.github.com/gabrielfalcao/20e567e188f588b65ba2)

This should be changed to ensure unique ports are being issued across all lambdas


env = Environment.from_string(data.get('awsEnvironment'))
    result = infra.get_lambda_code(func_name=functionName, env=env)
    return jsonify(result)
@app.route('/health')
def health():
    result = {'status': 'OK'}
    return jsonify(result)
@app.route('/')
def hello():
    return render_template('index.html')
@app.route('/<path:path>')
def send_static(path):
    return send_from_directory(web_dir + '/', path)
def get_payload():
    return json.loads(common.to_str(request.data))
def ensure_webapp_installed():
    web_dir = os.path.realpath(os.path.join(os.path.dirname(__file__), 'web'))
    node_modules_dir = os.path.join(web_dir, 'node_modules', 'jquery')
    if not os.path.exists(node_modules_dir):
        print('Initializing installation of Web application (this could take a long time, please be patient)')
        common.run('cd "%s"; npm install' % web_dir)
def serve(port):
    ensure_webapp_installed()
    load_plugins()
    canonicalize_api_names()
    backend_url = 'http://localhost:%s' % port
    config.USE_SSL = True
    services_infra.start_proxy(config.PORT_WEB_UI_SSL, backend_url)
    generic_proxy.serve_flask_app(app=app, port=port, quiet=True)