In #16217 we switched clients using Consul discovery to the `Status.Members`
endpoint for getting the list of servers so that we're using the correct
address. This endpoint has an authorization gate, so this fails if the anonymous
policy doesn't have `node:read`. We also can't check the `AuthToken` for the
request for the client secret, because the client hasn't yet registered so the
server doesn't have anything to compare against.
Instead of hitting the `Status.Peers` or `Status.Members` RPC endpoint, use the
Consul response directly. Update the `registerNode` method to handle the list of
servers we get back in the response; if we get a "no servers" or "no path to
region" response we'll kick off discovery again and retry immediately rather
than waiting 15s.
