dhcrelay does not obey -i interface option

[Jens Elkner]

If one starts dhcrelay with explicitly specifying the interfaces to listen,it silently ignores these options and still listens on all interfaces. This is neither what the man page says (it says, only if no interface is given, it listen on all interfaces), nor what is needed. It might be even considered being a security bug because dhcrelay listens on interfaces it shouldn't. Needless filter work causes unwanted overhead as well.

Wrt. the source package the patches/dhcrelay-listen.patch seems to be the root cause. It makes no sense at all to me ... Please explain or remove.