CURRENT panics sometimes

[Mark Tinguely]

We are chasing a different panic (kern/88725) where dynamic callout
are freed but the callout could be still pending. The freed memory
can be re-allocated, modified and then cause errors when the timer
wheel is checked.

After finding this one occurance, I did a complete search of callouts,
and I see a potential simular error in the ntoskrnl_libfini() routine
in the file /sys/compat/ndis/subr_ntoskrnl.c and a few other places
(7 total). I wanted to make verify each of these 7 occurances before
issuing a patch.

I suspect a simple test loop could verify that this is a simular error
as kern/88725.

--Mark Tinguely