MFC r196504:

MFC r196504:

  When moving ifnets from one vnet to another, and the ifnet
  has ifaddresses of AF_LINK type which thus have an embedded
  if_index "backpointer", we must update that if_index backpointer
  to reflect the new if_index that our ifnet just got assigned.

  This change affects only options VIMAGE builds.

  Submitted by: bz
  Reviewed by:  bz
  Approved by:  re (rwatson), julian (mentor)

Approved by:	re (rwatson)

git-svn-id: svn://svn.freebsd.org/base/stable/8@196624 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f