Don't lard up InternalClient with extra middleware

One can argue that it makes sense for the client-facing proxy server
to have certain middlewares like gatekeeper in its pipeline, but that
is not desirable for InternalClient. In particular, it prevents you
from passing in sysmeta headers using InternalClient, and I found
myself wanting to do that earlier today.

Now InternalClient's proxy application gets exactly what's configured;
no more, no less. This will mean that the object expirer can read and
write sysmeta headers, but I think we can trust it to keep our
secrets.

Change-Id: I17b4a89c24e600754701ee1645b40406421fa6f3
Merge "Don't lard up InternalClient with extra middleware"