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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


import os
import localstack_client.config
VERSION = '0.10.3'
REGION_LOCAL = 'local'
ENV_DEV = 'dev'
DEFAULT_PORT_APIGATEWAY_BACKEND = 4566
DEFAULT_PORT_KINESIS_BACKEND = 4565
DEFAULT_PORT_DYNAMODB_BACKEND = 4564
DEFAULT_PORT_S3_BACKEND = 4563
DEFAULT_PORT_SNS_BACKEND = 4562
DEFAULT_PORT_SQS_BACKEND = 4561
DEFAULT_PORT_ELASTICSEARCH_BACKEND = 4560
DEFAULT_PORT_CLOUDFORMATION_BACKEND = 4559
DEFAULT_PORT_STEPFUNCTIONS_BACKEND = 4558
DEFAULT_PORT_IAM_BACKEND = 4557
DEFAULT_PORT_EC2_BACKEND = 4556
DEFAULT_PORT_WEB_UI = 8080
LOCALHOST = 'localhost'
LOCALSTACK_MAVEN_VERSION = '0.1.22'