BUG/MINOR: log: fix outgoing abns address family

BUG/MINOR: log: fix outgoing abns address family

While reviewing the code in an attempt to fix GH #2875, I stumbled
on another case similar to aac570c ("BUG/MEDIUM: uxst: fix outgoing
abns address family in connect()") that caused abns(z) addresses to
fail when used as log targets.

The underlying cause is the same as aac570c, which is the rework of the
unix socket families in order to support custom addresses for different
adressing schemes, where a real_family() was overlooked before passing
a haproxy-internal address struct to socket-oriented syscall.

To fix the issue, we first copy the target's addr, and then leverage
real_family() to set the proper low-level address family that is passed
to sendmsg() syscall.

It should be backported in 3.1