Change all occurrences of zero_addr(&ss,AF_INET) to

Change all occurrences of zero_addr(&ss,AF_INET) to
zero_addr(&ss). All current uses were always of the
AF_INET form, so simplify the call. If in the future
we need to zero an addr to AF_INET6 this can be
done separately.
Jeremy.
(This used to be commit 2e92418a138bf2738b77b7e0fcb2fa37ad84fc0c)