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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


if isinstance(j, str):
            j = json.loads(j)
        self.__dict__.update(j)
    def to_dict(self):
        return json.loads(self.to_json())
    @classmethod
    def from_json(cls, j):
        j = JsonObject.as_dict(j)
        result = cls()
        result.apply_json(j)
        return result
    @classmethod
    def from_json_list(cls, l):
        return [cls.from_json(j) for j in l]
    @classmethod
    def as_dict(cls, obj):
        if isinstance(obj, dict):
            return obj
        return obj.to_dict()
    def __str__(self):
        return self.to_json()
    def __repr__(self):
        return self.__str__()
class CaptureOutput(object):