[PATCH] Fix CSRF verification on /api/varnish/purge & misc

Hi list,

Three more patches:

0001-Update-ssl_required-decorator-to-play-nice-with-othe.patch

This is the important one to make /api/varnish/purge/ work again. The
@ssl_required decorator now cooperates with other decorators and
retains attributes, rather than overriding them all.

The other 2 decorators in util/decorators.py probably also need this
fix, but I decided not to do it now to reduce testing effort.

0002-Fix-small-bug-in-api_varnish_purge-error-path.patch

Insignificant: return HttpResponse instead of raising it in error path.

0003-CSRF-verification-failure-now-returns-HTTP-403-Forbi.patch

The CSRF failure view previously returned with HTTP status 200 OK.
That's wrong -- apps and browsers should be signaled that the request
failed. Now returns 403 Forbidden.

Regards,
Marti