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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


for t in threading.enumerate():
        print(t)
    print(run("ps aux | grep 'node\\|java\\|python'"))
def merge_recursive(source, destination):
    for key, value in source.items():
        if isinstance(value, dict):
            
            node = destination.setdefault(key, {})
            merge_recursive(value, node)
        else:
            if not isinstance(destination, dict):
                LOG.warning('Destination for merging %s=%s is not dict: %s' %
                    (key, value, destination))
            destination[key] = value
    return destination
def merge_dicts(*dicts, **kwargs):
    """ Merge all dicts in `*dicts` into a single dict, and return the result. If any of the entries
        in `*dicts` is None, and `default` is specified as keyword argument, then return `default`. """
    result = {}
    for d in dicts:
        if d is None and 'default' in kwargs:
            return kwargs['default']
        if d:
            result.update(d)
    return result
def recurse_object(obj, func, path=''):