[api]auth_strategy defaults to `keystone`. The only other choice is
`noauth2`, which activates noauth paste pipelines, which go through
NoAuthMiddleware, which is crusty and bogus. It is used in our
functional tests to avoid having to fixture out keystone, but should not
be used in real deployments, ever. Deprecate the option for removal, and
add a deprecation warning in the paste pipeline if it is used.
When we remove the option, we could just hardcode to `keystone`. At that
time, we also need to move the middleware under the nova.tests package
-- or find a way to get rid of it entirely by instead stubbing out
keystone in tests if that's relatively easy.
Change-Id: I9e2be5423cc0821a628db7a68ad52bbd91264acd
18de63deaa