The proto-libnv implementation embedded in hastd pads names and values
out to the nearest multiple of eight bytes, but leaves the padding
uninitialized, leaking up to 14 bytes of recycled heap per pair in a
message.
While here, switch from bcopy() to memcpy().
MFC after: 3 days
Reviewed by: kevans, emaste
Differential Revision: https://reviews.freebsd.org/D59343
Dag-Erling Smørgrav
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