dnsmasq: a) Fix start-up order for making DHCPv6 DUID.
Previously, if the DUID wasn't read from the lease-file or script, a new
one was created _after_ the helper process fork, so for that first run,
the script calls got an empty DUID.
Also, use a DUID_LL format DUID when there's no stable lease storage,
as well as when the RTC is broken. That has a chance of evaluating to
the same value on each startup.
b) Fix FTBFS on openBSD-current.