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
```
import os
import re
import json
import time
import boto3
import base64
import logging
import six
from localstack import config
from localstack.constants import (
    REGION_LOCAL, LOCALHOST, MOTO_ACCOUNT_ID, ENV_DEV, APPLICATION_AMZ_JSON_1_1,
    APPLICATION_AMZ_JSON_1_0, APPLICATION_X_WWW_FORM_URLENCODED, TEST_AWS_ACCOUNT_ID)
from localstack.utils.common import (
    run_safe, to_str, is_string, is_string_or_bytes, make_http_request, is_port_open, get_service_protocol)
from localstack.utils.aws.aws_models import KinesisStream
ENV_ACCESS_KEY = 'AWS_ACCESS_KEY_ID'
ENV_SECRET_KEY = 'AWS_SECRET_ACCESS_KEY'
ENV_SESSION_TOKEN = 'AWS_SESSION_TOKEN'
LOG = logging.getLogger(__name__)
LOCAL_REGION = None
CUSTOM_BOTO3_SESSION = None
CREATE_NEW_SESSION_PER_BOTO3_CONNECTION = False
INITIAL_BOTO3_SESSION = None
BOTO_CLIENTS_CACHE = {}
DEFAULT_TIMER_LOOP_SECONDS = 60 * 50
class Environment(object):