fix incorrect real ip for ssl-passthrough 1. this implemention can work together with 'use-forwarded-for: "true"' and 'compute-full-forwarded-for: "true"'. 2. this fix breaks function of 'use-proxy-protocol: "true"' 3. this fix can not be cherrypicked to latest ingress-nginx, because 9af574a (>=0.26.0) refactor the real ip code in nginx.tmpl Signed-off-by: Huanle Han <hanhuanle@caicloud.io>