http_client: x-forwarded-for controls X-Forwarded-For presence

http_client: x-forwarded-for controls X-Forwarded-For presence

If x-forwarded-for setting (boolean) is enabled, http_client will
generate an X-Forwarded-For header entry which includes existing
X-Forwarded-For (if any) and current peer address (immediate client
of Metaproxy). By default x-forwarded-for disabled and X-Forwarded-For
will not be generated.