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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


return ''
            
            container_name = self.get_container_name(func_arn)
            docker_cmd = self._docker_cmd()
            
            LOG.debug('Getting container network: %s' % container_name)
            cmd = (
                '%s inspect %s'
                ' --format "{{ .HostConfig.NetworkMode }}"'
            ) % (docker_cmd, container_name)
            LOG.debug(cmd)
            cmd_result = run(cmd, asynchronous=False, stderr=subprocess.PIPE, outfile=subprocess.PIPE)
            container_network = cmd_result.strip()
            return container_network
    def idle_container_destroyer(self):
        """
        Iterates though all the lambda containers and destroys any container that has
        been inactive for longer than MAX_CONTAINER_IDLE_TIME_MS.
        :return: None
        """
        LOG.info('Checking if there are idle containers.')
        current_time = int(time.time() * 1000)
        for func_arn, last_run_time in dict(self.function_invoke_times).items():
            duration = current_time - last_run_time
            
            if duration < MAX_CONTAINER_IDLE_TIME_MS:
                continue
            
            self.destroy_docker_container(func_arn)
    def start_idle_container_destroyer_interval(self):