<!-- 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


self.assertEqual('Disabled', getResult['State'])
    def test_publish_function_version(self):
        with self.app.test_request_context():
            self._create_function(self.FUNCTION_NAME)
            result = json.loads(lambda_api.publish_version(self.FUNCTION_NAME).get_data())
            result2 = json.loads(lambda_api.publish_version(self.FUNCTION_NAME).get_data())
            result.pop('RevisionId', None)  
            result2.pop('RevisionId', None)  
            expected_result = dict()
            expected_result['CodeSize'] = self.CODE_SIZE
            expected_result['CodeSha256'] = self.CODE_SHA_256
            expected_result['FunctionArn'] = str(lambda_api.func_arn(self.FUNCTION_NAME)) + ':1'
            expected_result['FunctionName'] = str(self.FUNCTION_NAME)
            expected_result['Handler'] = str(self.HANDLER)
            expected_result['Runtime'] = str(self.RUNTIME)
            expected_result['Timeout'] = self.TIMEOUT
            expected_result['Description'] = ''
            expected_result['MemorySize'] = self.MEMORY_SIZE
            expected_result['Role'] = self.ROLE
            expected_result['LastModified'] = self.LAST_MODIFIED
            expected_result['TracingConfig'] = self.TRACING_CONFIG
            expected_result['Version'] = '1'
            expected_result2 = dict(expected_result)
            expected_result2['FunctionArn'] = str(lambda_api.func_arn(self.FUNCTION_NAME)) + ':2'
            expected_result2['Version'] = '2'
            self.assertDictEqual(expected_result, result)
            self.assertDictEqual(expected_result2, result2)
    def test_publish_non_existant_function_version_returns_error(self):
        with self.app.test_request_context():
            result = json.loads(lambda_api.publish_version(self.FUNCTION_NAME).get_data())