We shouldn't be replacing the configured server address on agents. Doing
so breaks the agent's ability to fall back to the fixed registration
endpoint when all servers are down, since we replaced it with the first
discovered apiserver address. The fixed registration endpoint will be
restored as default when the service is restarted, but this is not the
correct behavior. This should have only been done on etcd-only nodes
that start up using their local supervisor, but need to switch to a
control-plane node as soon as one is available.
Signed-off-by: Brad Davidson <brad.davidson@rancher.com>