Do address assignment/removal operations after callbacks. Presently,
ifconfig callbacks are used for L2 configuration, media and vlan,
so actions associated with address assignment, like sending out a
gratuitous ARP, should go when L2 is running already.
Return ifvlan.c to the state of rev. 1.7.2.2 -- undo the last
back-out. The above change to ifconfig.c lets us use a callback
for vlan set-up without facing the evil side-effects from IP
assignment to an orphaned vlan interface.
Approved by: re (scottl)
af897e152b