Add support for endpoints without scheme or as bare hostname.
containerd supports this, but wharfie has not historically allowed for this.
Don't set ns param if the request is not being proxied.
Some namespace-aware registries have problems handling the request if the ns parameter is set to the same value as the hostname. We should only set the ns parameter when the request is being sent to a non-default endpoint.
internal-ref: SURE-7640