MEDIUM: http: Ignore http-tunnel option on backend

This option is frontends specific, so there is no reason to support it on
backends. So now, it is ignored if it is set on a backend and a warning is
emitted during the startup. The change is quite trivial, but the commit is
tagged as MEDIUM because it is a small breakage with previous versions and
configurations using this options could emit a warning now.
2 files changed