MFC r324644 (by imp):

MFC r324644 (by imp):
Closer examination shows that nvme and CAM both normally zero-fill
allocations (for req and ccb, which ultimately contain the
nvme_cmd). As such, we can micro-optimize these routines. Add a
comment to this effect, and bzero the ccb used to make the requests
for the nda dump rotuine so it more closely matches a ccb allocated
with xpt_get_ccb().