<!-- Love localstack? Please consider supporting our collective:
👉  https://opencollective.com/localstack/donate -->
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


""" This method must be overwritten by subclasses. """
        raise Exception('Not implemented.')
    def startup(self):
        pass
    def cleanup(self, arn=None):
        pass
    def _store_logs(self, func_details, log_output, invocation_time):
        if not aws_stack.is_service_enabled('logs'):
            return
        logs_client = aws_stack.connect_to_service('logs')
        log_group_name = '/aws/lambda/%s' % func_details.name()
        time_str = time.strftime('%Y/%m/%d', time.gmtime(invocation_time))
        log_stream_name = '%s/[$LATEST]%s' % (time_str, short_uid())
        
        log_groups = logs_client.describe_log_groups()['logGroups']
        log_groups = [lg['logGroupName'] for lg in log_groups]
        if log_group_name not in log_groups:
            logs_client.create_log_group(logGroupName=log_group_name)
        
        logs_client.create_log_stream(logGroupName=log_group_name, logStreamName=log_stream_name)
        
        invocation_time = invocation_time
        finish_time = int(time.time() * 1000)
        log_lines = log_output.split('\n')
        time_diff_per_line = float(finish_time - invocation_time) / float(len(log_lines))
        log_events = []
        for i, line in enumerate(log_lines):
            if not line: