Adapt the configuration of redirects from the server hosting libvirt.org

The redirect to the 'libvirt-console-proxy' Golang module is not adapted
as it doesn't exist on the current server.

NOTES:
 - The redirects are currently configured for hosting via the
   'gitlab.io/libvirt' URI. For hosting via custom domain it will need
   to be rewritten to drop the '/libvirt' prefixes.

 - gitlab pages doesn't currently support redirects to outside content,
   thus most of the redirects don't actually work:

     gitlab-org/gitlab-pages#601

 - The redirects file is only installed in the webpage job but is not
   actually distributed.

 - The validity of the redirects can be checked by visiting:

     https://libvirt.gitlab.io/_redirects



   Having them installed allows us to validate them before we'll be
   switching to use gitlab pages completely.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Daniel P. Berrangé <b...