We usually want to have ratelimit fairly far left in the pipeline -- the
assumption is that something like an auth check will be fairly expensive
and we should try to shield the auth system so it doesn't melt under the
load of a misbehaved swift client.
But with S3 requests, we can't know the account/container that a request
is destined for until *after* auth. Fortunately, we've already got some
code to make s3api play well with ratelimit.
So, let's have our cake and eat it, too: allow operators to place
ratelimit once, before auth, for swift requests and again, after auth,
for s3api. They'll both use the same memcached keys (so users can't
switch APIs to effectively double their limit), but still only have each
S3 request counted against the limit once.
Change-Id: If003bb43f39427fe47a0f5a01dbcc19e1b3b67ef