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# Type of request: This is a bug report

# Detailed description
When running a java lambda in localstack with `LAMBDA_EXECUTOR=docker` and  `LAMBDA_JAVA_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005"` (replaced `_debug_port_` with `5005`), the port is not opened in the lambda execution docker container.

Looking at `Util.get_java_opts` in `localstack/services/awslambda/lambda_executors.py`, `debug_java_port` is not set in case `_debug_port_` is set

```
class Util:
    debug_java_port = False

    @classmethod
    def get_java_opts(cls):
        opts = config.LAMBDA_JAVA_OPTS or ''
        if '_debug_port_' in opts:
            if not cls.debug_java_port:
                cls.debug_java_port = get_free_tcp_port() ### <<< debug_java_port is only set here
            opts = opts.replace('_debug_port_', ('%s' % cls.debug_java_port))
        ### In other case, `cls.debug_java_port` is not set.
        return opts
```
## Expected behavior

`debug_java_port` should be set to the configured port

## Actual behavior

`debug_java_port` is empty

# Steps to reproduce
docker-compose file
```
version: '2.1'
services:
  localstack:
    container_name: localstack
    image: localstack/localstack
    privileged: true
    ports:
      - "4567-4582:4567-4582"
      - "9070:9070"
    environment:
      SERVICES: sqs,lambda
      DOCKER_HOST: unix:///var/run/docker.sock
      PORT_WEB_UI: 9070
      LAMBDA_EXECUTOR: docker
      LAMBDA_JAVA_OPTS: "-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005"
      DEBUG: 1
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /tmp/localstack:/tmp/localstack
```

## Command used to start LocalStack

`docker-compose up`


if lambda_cwd:
                os.chdir(lambda_cwd)
            if environment:
                os.environ.update(environment)
            result = lambda_function(event, context)
            queue.put(result)
        process = Process(target=do_execute)
        with CaptureOutput() as c:
            process.run()
        result = queue.get()
        
        log_output = ''
        for stream in (c.stdout(), c.stderr()):
            if stream:
                log_output += ('\n' if log_output else '') + stream
        
        _store_logs(func_details, log_output)
        return result
    def execute_java_lambda(self, event, context, main_file, func_details=None):
        handler = func_details.handler
        opts = config.LAMBDA_JAVA_OPTS if config.LAMBDA_JAVA_OPTS else ''
        event_file = EVENT_FILE_PATTERN.replace('*', short_uid())
        save_file(event_file, json.dumps(event))
        TMP_FILES.append(event_file)
        class_name = handler.split('::')[0]
        classpath = '%s:%s:%s' % (LAMBDA_EXECUTOR_JAR, main_file, Util.get_java_classpath(main_file))
        cmd = 'java %s -cp %s %s %s %s' % (opts, classpath, LAMBDA_EXECUTOR_CLASS, class_name, event_file)
        LOG.warning(cmd)
        result = self.run_lambda_executor(cmd, func_details=func_details)