shutting down -- this is only supposed to happen from the pcmcia
kernel thread while the system is running
-in wd_shutdown, call ata_addref first, so that the adapter is either
active or we know that it isn't
This fixes a hang on shutdown-p reported by Dennis den Brok per
PR kern/40531. Verified by by Dennis and me.
(reported against 5.0-Beta, so this is a pullup candidate)
37d6396041