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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


continue
            
            log_time = invocation_time + float(i) * time_diff_per_line
            event = {'timestamp': int(log_time), 'message': line}
            log_events.append(event)
        if not log_events:
            return
        logs_client.put_log_events(
            logGroupName=log_group_name,
            logStreamName=log_stream_name,
            logEvents=log_events
        )
    def run_lambda_executor(self, cmd, event=None, env_vars={}):
        process = run(cmd, asynchronous=True, stderr=subprocess.PIPE, outfile=subprocess.PIPE, env_vars=env_vars,
                      stdin=True)
        result, log_output = process.communicate(input=event)
        result = to_str(result).strip()
        log_output = to_str(log_output).strip()
        return_code = process.returncode
        
        
        
        if '\n' in result:
            additional_logs, _, result = result.rpartition('\n')
            log_output += '\n%s' % additional_logs
        if return_code != 0:
            raise Exception('Lambda process returned error status code: %s. Output:\n%s' %
                (return_code, log_output))
        return result, log_output
class ContainerInfo: