sqs.changeMessageVisibility according to [this](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_ChangeMessageVisibility.html#API_ChangeMessageVisibility_Examples) makes a request directly to the Queue's URL rather than via the SQS Endpoint. (I'm already setting SQS endpoint to LOCALSTACK_HOSTNAME - makes no difference for this call)..

In localstack the queue URL host returned is by default set to the value of HOSTNAME_EXTERNAL, which I'm setting to localstack, but calling this method within a lambda, does not work and I get the error:

```
UnknownEndpoint: Inaccessible host: `localstack'. This service may not be available in the `us-east-1' region. 
```

So, how can I make the queue URL accessible from within a lambda using localstack? Effectively I need to make **http://localstack** accessible from within lambda.

I'm using the following cmd to start localstack:

```
LAMBDA_EXECUTOR=docker-reuse DEBUG=1 LAMBDA_REMOTE_DOCKER=0 DATA_DIR=/tmp/localstack/data HOSTNAME_EXTERNAL=localstack localstack start
```
from localstack.utils.aws import aws_stack
from localstack.utils.common import to_str, md5, clone
from localstack.utils.analytics import event_publisher
from localstack.services.awslambda import lambda_api
from localstack.services.generic_proxy import ProxyListener
XMLNS_SQS = 'http://queue.amazonaws.com/doc/2012-11-05/'
SUCCESSFUL_SEND_MESSAGE_XML_TEMPLATE = """
    <?xml version="1.0"?>
    <SendMessageResponse xmlns="%s">
        <SendMessageResult>
            <MD5OfMessageAttributes>{message_attr_hash}</MD5OfMessageAttributes>
            <MD5OfMessageBody>{message_body_hash}</MD5OfMessageBody>
            <MessageId>{message_id}</MessageId>
        </SendMessageResult>
        <ResponseMetadata>
            <RequestId>00000000-0000-0000-0000-000000000000</RequestId>
        </ResponseMetadata>
    </SendMessageResponse>
""".strip() % XMLNS_SQS
VALID_ATTRIBUTE_NAMES = ['DelaySeconds', 'MaximumMessageSize', 'MessageRetentionPeriod',
                         'ReceiveMessageWaitTimeSeconds', 'RedrivePolicy', 'VisibilityTimeout',
                         'ContentBasedDeduplication', 'KmsMasterKeyId', 'KmsDataKeyReusePeriodSeconds',
                         'CreatedTimestamp', 'LastModifiedTimestamp', 'FifoQueue',
                         'ApproximateNumberOfMessages', 'ApproximateNumberOfMessagesNotVisible']
UNSUPPORTED_ATTRIBUTE_NAMES = [
    'DelaySeconds', 'MaximumMessageSize', 'MessageRetentionPeriod', 'Policy', 'RedrivePolicy',
    'ContentBasedDeduplication', 'KmsMasterKeyId', 'KmsDataKeyReusePeriodSeconds', 'FifoQueue'
]
QUEUE_ATTRIBUTES = {}
def parse_request_data(method, path, data):