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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


folder = new_tmp_file()
    rm_rf(folder)
    mkdir(folder)
    return folder
def is_ip_address(addr):
    try:
        socket.inet_aton(addr)
        return True
    except socket.error:
        return False
def is_zip_file(content):
    stream = BytesIO(content)
    return zipfile.is_zipfile(stream)
def unzip(path, target_dir):
    try:
        zip_ref = zipfile.ZipFile(path, 'r')
    except Exception as e:
        LOG.warning('Unable to open zip file: %s: %s' % (path, e))
        raise e
    
    
    for file_entry in zip_ref.infolist():
        _unzip_file_entry(zip_ref, file_entry, target_dir)
    zip_ref.close()
def _unzip_file_entry(zip_ref, file_entry, target_dir):