<!-- Love localstack? Please consider supporting our collective:
👉  https://opencollective.com/localstack/donate -->

# Type of request: This is a ...

- [x] bug report
- [ ] feature request

# Detailed description
I get a 404 when I request a file I uploaded via a HEAD request.
This only happens when using the new edge router port.
I think there's faulty logic in the edge router when looking at HEAD requests.

## Expected behavior

I expect the behavior I get from requesting via the dedicated S3 port (HTTP 200 if a file exists)

## Actual behavior

A 404 on HEAD request through the edge router port.

# Steps to reproduce
```
version: '2.2'

services:
  localstack:
    image: localstack/localstack
    ports:
      - '4566:4566'
    environment:
      - SERVICES=s3
      - HOSTNAME_EXTERNAL=s3.test

```
```
docker-compose up -d
```
Making a bucket and uploading a file:
```
AWS_ENDPOINT_URL=http://s3.test:4566
aws --endpoint-url=$AWS_ENDPOINT_URL s3 mb s3://attachments
aws --endpoint-url=$AWS_ENDPOINT_URL s3 cp test s3://attachments
```
Lastly, HEADing the file to see if it exists.
```
$ curl -I $AWS_ENDPOINT_URL/attachments/test -H 'Authorization: aaa'
HTTP/1.1 404 Not Found
Server: BaseHTTP/0.6 Python/3.8.2
Date: Wed, 03 Jun 2020 21:28:46 GMT
Content-Length: 21
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: HEAD,GET,PUT,POST,DELETE,OPTIONS,PATCH
Access-Control-Allow-Headers: authorization,content-type,content-md5,cache-control,x-amz-content-sha256,x-amz-date,x-amz-security-token,x-amz-user-agent,x-amz-target,x-amz-acl,x-amz-version-id,x-localstack-target,x-amz-tagging
Access-Control-Expose-Headers: x-amz-version-id
```
Localstack logs from requesting via *:4566
```
localstack_1  | Starting edge router (https port 4566)...
localstack_1  | Starting mock S3 service in http ports 4566 (recommended) and 4572 (deprecated)...
localstack_1  | 2020-06-03T21:04:36:INFO:localstack.multiserver: Starting multi API server process on port 38679
localstack_1  | Ready.
localstack_1  | 2020-06-03T21:04:41:INFO:localstack.utils.persistence: Restored 10 API calls from persistent file: /tmp/localstack/recorded_api_calls.json
localstack_1  | 2020-06-03T21:05:09:INFO:localstack.services.edge: Unable to find forwarding rule for host "s3.test:4566", path "/attachments/test", target header "", auth header ""
```

Switching the exposed port to 4572 and requesting through there gives me:
```
AWS_ENDPOINT_URL=http://s3.test:4572
```
```
$ curl -I $AWS_ENDPOINT_URL/attachments/test -H 'Authorization: aaa'
HTTP/1.1 200 OK
Server: BaseHTTP/0.6 Python/3.8.2
Date: Wed, 03 Jun 2020 21:39:38 GMT
Content-Type: binary/octet-stream
ETag: "d41d8cd98f00b204e9800998ecf8427e"
last-modified: Wed, 03 Jun 2020 21:31:11 GMT
Content-Length: 0
Access-Control-Allow-Origin: *
x-amz-request-id: 3144F10D603C9424
x-amz-id-2: MzRISOwyjmnup3144F10D603C94247/JypPGXLh0OVFGcJaaO3KW/hRAqKOpIEEp
Access-Control-Allow-Methods: HEAD,GET,PUT,POST,DELETE,OPTIONS,PATCH
Access-Control-Allow-Headers: authorization,content-type,content-md5,cache-control,x-amz-content-sha256,x-amz-date,x-amz-security-token,x-amz-user-agent,x-amz-target,x-amz-acl,x-amz-version-id,x-localstack-target,x-amz-tagging
Access-Control-Expose-Headers: x-amz-version-id
```
import io
import os
import re
import pwd
import grp
import sys
import json
import uuid
import time
import glob
import base64
import socket
import hashlib
import decimal
import logging
import tarfile
import zipfile
import binascii
import calendar
import tempfile
import threading
import subprocess
import six
import shutil
import requests
import dns.resolver