Work around the deadlock that occours when ATA waits for the taskqueue

Work around the deadlock that occours when ATA waits for the taskqueue
to call back for completition and something else is holding the taskqueue
waiting for ATA to return data.
This should clear up the "semaphore timeout !! DANGER Will Robinson !!"
in most situations, and log "taskqueue timeout - completing request directly"
instead, with a delayed "WARNING - freeing taskqueue zombie request" when
the taskqueue finally calls us back with the now stale request.
(It would have been nice if there was a way to remove a scheduled item from
 a taskqueue, but that is not currently implemented in the kernel).

A real fix for this is in the works but wont make it to 6.1RELEASE

definite MFC candidate.