Fix for EZP-22667: Response TTL should not depend on X-User-Hash

https://jira.ez.no/browse/EZP-22667

In the default view controller, setting the max age Cache-Control HTTP header is dependent on the request setting X-User-Hash. While context-aware cache and max age are related, they should be separate issues.
Some concrete reasons for treating them separately:

* In some cases the management of TTL is deferred to a separate team who is in charge of Apache or Varnish, not eZ Publish.
* For dev / debug purposes you want to see the TTL being used
* You should be able to set TTL regardless of whether your reverse proxy is setting a default X-User-Hash