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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


self.assertEqual(self.RESOURCENOTFOUND_EXCEPTION, result['__type'])
            self.assertEqual(self.RESOURCENOTFOUND_MESSAGE % lambda_api.func_arn(self.FUNCTION_NAME),
                             result['message'])
    def test_list_function_versions(self):
        with self.app.test_request_context():
            self._create_function(self.FUNCTION_NAME)
            lambda_api.publish_version(self.FUNCTION_NAME)
            lambda_api.publish_version(self.FUNCTION_NAME)
            result = json.loads(lambda_api.list_versions(self.FUNCTION_NAME).get_data())
            for version in result['Versions']:
                
                version.pop('RevisionId', None)
            latest_version = dict()
            latest_version['CodeSize'] = self.CODE_SIZE
            latest_version['CodeSha256'] = self.CODE_SHA_256
            latest_version['FunctionArn'] = str(lambda_api.func_arn(self.FUNCTION_NAME)) + ':$LATEST'
            latest_version['FunctionName'] = str(self.FUNCTION_NAME)
            latest_version['Handler'] = str(self.HANDLER)
            latest_version['Runtime'] = str(self.RUNTIME)
            latest_version['Timeout'] = self.TIMEOUT
            latest_version['Description'] = ''
            latest_version['MemorySize'] = self.MEMORY_SIZE
            latest_version['Role'] = self.ROLE
            latest_version['LastModified'] = self.LAST_MODIFIED
            latest_version['TracingConfig'] = self.TRACING_CONFIG
            latest_version['Version'] = '$LATEST'
            version1 = dict(latest_version)
            version1['FunctionArn'] = str(lambda_api.func_arn(self.FUNCTION_NAME)) + ':1'
            version1['Version'] = '1'
            version2 = dict(latest_version)