Destroy cloned interfaces at netif stop, netif restart and shutdown.

Destroy cloned interfaces at netif stop, netif restart and shutdown.
This is especially important during shutdown because a child interface
of lagg with WOL enabled will not enable WOL at interface shutdown and
thus no WOL to wake up the device (and machine).

PR:		158734, 109980
Reported by:	Antonio Huete Jimenez <tuxillo at quantumachine.net>
		Marat N.Afanasyev <marat at zealot.ksu.ru>
reviewed by:	kp
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D26797