Merge from stable/9 SVN r250927: MFC: r249628, r249742

Merge from stable/9 SVN r250927: MFC: r249628, r249742

- recover missing arp_ifinit() call.
- plug static llentry leak (ipv4 & ipv6 were affected).

PR:		kern/172985

Also merge from stable/9 SVN r240313:

Merge r238990 (manually resolving absence of r237263):
  Fix races between in_lltable_prefix_free(), lla_lookup(),
  llentry_free() and arptimer():

  o Use callout_init_rw() for lle timeout, this allows us safely
    disestablish them.
    - This allows us to simplify the arptimer() and make it
      race safe.
  o Consistently use ifp->if_afdata_lock to lock access to
    linked lists in the lle hashes.
  o Introduce new lle flag LLE_LINKED, which marks an entry that
    is attached to the hash.
    - Use LLE_LINKED to avoid double unlinking via consequent
      calls to llentry_free().
    - Mark lle with LLE_DELETED via |= operation istead of =,
      so that other flags won't be lost.
  o Make LLE_ADDREF(), LLE_REMREF() and LLE_FREE_LOCKED() more
    consistent and provide more informative KASSERTs.

  The patch is a collaborative work of all submitters and myself.

  PR:		kern/165863
  Submitted by:	zont, rstone
  Submitted by:	Eric van Gyzen <eric_van_gyzen dell.com>

git-svn-id: svn://svn.freebsd.org/base/stable/8@255470 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f