MFH 295796 (based on)
Fix regression introduced on 272446r. lagg(4) supports the protocol none,
where it disables any traffic without disabling the lagg(4) interface itself.

PR: 206478
Submitted by: Erin Clark <erin.clark.ix@gmail.com>
Reviewed by: rpokala, bapt
Approved by: re (glebius)
Differential Revision: https://reviews.freebsd.org/D5188