Revision 368346

Revert r366857.

r366857 created a number of problems, tearing down interfaces too
early in shutdown. This resulted in:

- hung ssh sessions when shutting down or rebooting remotely using
  shutdown (I've used exec shutdown, for years, as apposed to simply
  shutdown).

- NFS mounted filesystems "disappear" prior to unmount.

- dhclient attached to a VLAN on an interface who's parent interface
  has already shut down prints errors.

The path forward is to teach lagg(4) and vlan(4) about WOL.

PR:		251531, 251540
PR:		158734, 109980 are broken again
Reported by:	jhb, emaste, jtl, Helge Oldach<freebsd_oldach.net>
		Martin Birgmeier <d8zNeCFG_aon.at>
Discussion at:	https://reviews.freebsd.org/D27459