Fix domain swapping

Applies to https://github.com/GigaOM/gigaom/issues/5362

For environments like VIP where the admin ajax url is/can be different from the front end url, we need to do a little dance to make sure it doesn't get changed on the links causing the issue reported.
Here's a simpler regex:

```js
var url_pattern = new RegExp( '(https?)://([^/]+)' );
```