[CACHE] Loading images from non-standard port does not work if page gets cached

### Description

If an image source points to a non-default port, the redirect built by the amp cache services points to non-existing host names and therefore no images are displayed if the page gets cached on google infrastructure.

### Reproduction Steps

1. Set an image source that does include a port number. Like

```

```

2. Get the page cached. This changes the Tag to ``
3. This `src` creates a request that contains a `location` header: `location: https://api-energate-de:81.cdn.ampproject.org/i/s/api.energate.de:81/assets/images/35509.jpg` - So it basically breaks the URI by including a colon into the host name and cannot redirect to that host.

* amp source page: https://amp.energate.de/217567
* Cached version with broken image: https://amp-energate-de.cdn.ampproject.org/c/s/amp.energate.de/217567

### Relevant Logs

```shell
From Console:

GET https://api-energate-de.cdn.ampproject.org/i/s/api.energate.de:81/assets/images/35509.jpg net::ERR_INVALID_REDIRECT

Full Response Headers for request of `https://api-energate-de.cdn.ampproject.org/i/s/api.energate.de:81/assets/images/35509.jpg` (line beginning with `#` included by me):

alt-svc: h3=":443"; ma=2592000,h3-29=":443"; ma=2592000,h3-Q050=":443"; ma=2592000,h3-Q046=":443"; ma=2592000,h3-Q043=":443"; ma=2592000,quic=":443"; ma=2592000; v="46,43"
cache-control: private
content-length: 289
content-type: text/html; charset=UTF-8
date: Fri, 26 Nov 2021 09:35:34 GMT
location: https://api-energate-de:81.cdn.ampproject.org/i/s/api.energate.de:81/assets/images/35509.jpg
# ^ fails
server: sffe
x-content-type-options: nosniff
x-xss-protection: 0
```

### Browser(s) Affected

_No response_

### OS(s) Affected

_No response_

### Device(s) Affected

_No response_

### AMP Version Affected

2111060251009

Start with the AMP cache image URL and redirect behavior described in the reproduction steps, using the supplied source and cached page URLs. Trace how a non-default port is incorporated into the redirect and verify that the cached image request produces a valid host and loads successfully.

Written by the indexing model from the issue text.