Expose groups by default in ifconfig output. This was never hidden by
OpenBSD; unsure why we chose to do so. As groups are a requirement for
pf, exposing them by default will make our pf implementation less
confusing.

While here add a missing free() that OpenBSD fixed 7 years ago.

PR:		194925
Differential Revision:	https://reviews.freebsd.org/D1185
Approved by:	des
Obtained from:	OpenBSD