BSD: ignore default loopback interface

lo0 is the default loopback interface on {Free,Open,Net}BSD, I think it makes sense to ignore it like lo on Linux.

Before:
/cf-promises -v|awk '/Hard classes/ {for (i=7;i<=NF;i++) {print $i}}'|grep net_iface
net_iface_em0
net_iface_gif0
net_iface_le0
net_iface_lo0


After:
cf-promises -v|awk '/Hard classes/ {for (i=7;i<=NF;i++) {print $i}}'|grep net_iface
net_iface_em0
net_iface_gif0
net_iface_le0