Previously there was a default controller URL in the proxy. This
default was never used for any proxy injected by `conduit inject` and
it was the wrong default when using the proxy outside of Kubernetes.
Also more generally this is such an important setting in terms of
correctness and security that it was dangerous to let it be implied in
any context.
Remove the default, requiring that it be set in order for the proxy to
start.
f1a4e98053