Plug reference leaks in the link-layer code ("new-arp") that previously
prevented the link-layer entry from being freed.
In both in.c and in6.c (though that code path seems to be basically dead)
plug a reference leak in case of a pending callout being drained.
In if_ether.c consistently add a reference before resetting the callout
and in case we canceled a pending one remove the reference for that.
In the final case in arptimer, before freeing the expired entry, remove
the reference again and explicitly call callout_stop() to clear the active
flag.
In nd6.c:nd6_free() we are only ever called from the callout function and
thus need to remove the reference there as well before calling into
llentry_free().
In if_llatbl.c when freeing the entire tables make sure that in case we
cancel a pending callout to remove the reference as well.
Reviewed by: qingli (earlier version)
MFC after: 10 days
Problem observed, patch tested by: simon on ipv6gw.f.o,
Christian Kratzer (ck cksoft.de),
Evgenii Davidov (dado korolev-net.ru)
PR: kern/144564
Configurations still affected: with options FLOWTABLE
e36601cbc0