The Mobile content service seems to disregard domains from the Beta Cluster:
```
$ curl -v localhost:6927/en.wikipedia.org/v1/page/mobile-html/Foobar
> GET /en.wikipedia.org/v1/page/mobile-html/Foobar HTTP/1.1
> User-Agent: curl/7.38.0
> Host: localhost:6927
> Accept: */*
>
< HTTP/1.1 200 OK
< Access-Control-Allow-Origin: *
< Access-Control-Allow-Headers: Accept, X-Requested-With, Content-Type
< X-XSS-Protection: 1; mode=block
< X-Content-Type-Options: nosniff
< X-Frame-Options: SAMEORIGIN
< Content-Security-Policy: default-src 'self'; object-src 'none'; media-src *; img-src *; style-src *; frame-ancestors 'self'
< X-Content-Security-Policy: default-src 'self'; object-src 'none'; media-src *; img-src *; style-src *; frame-ancestors 'self'
< X-WebKit-CSP: default-src 'self'; object-src 'none'; media-src *; img-src *; style-src *; frame-ancestors 'self'
< Content-Type: text/html; charset=utf-8
< Vary: Accept-Encoding
< Date: Wed, 23 Sep 2015 22:04:00 GMT
< Connection: keep-alive
< Transfer-Encoding: chunked
$ curl -v localhost:6927/en.wikipedia.beta.wmflabs.org/v1/page/mobile-html/Foobar
> GET /en.wikipedia.beta.wmflabs.org/v1/page/mobile-html/Foobar HTTP/1.1
> User-Agent: curl/7.38.0
> Host: localhost:6927
> Accept: */*
>
< HTTP/1.1 404 Not Found
< Access-Control-Allow-Origin: *
< Access-Control-Allow-Headers: Accept, X-Requested-With, Content-Type
< X-XSS-Protection: 1; mode=block
< X-Content-Type-Options: nosniff
< X-Frame-Options: SAMEORIGIN
< Content-Security-Policy: default-src 'self'; object-src 'none'; media-src *; img-src *; style-src *; frame-ancestors 'self'
< X-Content-Security-Policy: default-src 'self'; object-src 'none'; media-src *; img-src *; style-src *; frame-ancestors 'self'
< X-WebKit-CSP: default-src 'self'; object-src 'none'; media-src *; img-src *; style-src *; frame-ancestors 'self'
< Content-Type: application/json; charset=utf-8
< Content-Length: 222
< Vary: Accept-Encoding
< Date: Wed, 23 Sep 2015 22:04:24 GMT
< Connection: keep-alive
```
It needs to work well for `*.wikipedia.beta.wmflabs.org` domains as well, since the Beta Cluster is where we test the integration of various services.