Fix EZP-22073: long sub-request fragment urls caused by serialized_siteaccess.

JIRA Issue: https://jira.ez.no/browse/EZP-22073

Description:
When performing sub-requests with hinclude, the siteaccess information is serialized and used in the url. 
The problem is that a configuration with a large number of siteaccess may generate very long fragment urls as well; for example using map/host:
```
ezpublish:
    siteaccess:
        match:
            Map\Host:
                www.domian.tld: my_siteaccess
                ...  long list of domains / siteaccesses ...
```

Serializing the siteaccess information is not required, as it can be rebuilt in ```SiteAccessMatchListener```