An all-zero DUID is considered to be a blank DUID - ensure that we do not generate one.
An all-zero DUID is considered to be a blank DUID - ensure that we do not
generate one.

ok krw@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars