first_boot_pending() is true while /firstboot exists on FreeBSD. A FreeBSD
cloud image upgrades its base system on its first boot, starts sshd only
after that and restarts right away, and /etc/rc removes /firstboot just
before that restart. netOrk waits for this before it sets up a new VM
(NetOrk/netork#795).
OpenBSD has no such marker to ask yet, so it returns False there.
netOrk reads an empty update list as "no updates" and closes every patch
clock on the host. A refused sudo, a failing pkg, syspatch or freebsd-update,
or a pkg database pkg cannot read used to come back as that empty list. Each
of these now raises. Only pkg's "is not installed" still means no packages.
BsdDriver takes on napalm-device-types' HostStatusMixin. On FreeBSD it
reports a host whose installed kernel differs from the running one as
needing a reboot (device-types 4.1). OpenBSD stays unknown.
Closes#4