Review fixes. The first-boot systemd-analyze now waits (bounded) for
startup to finish, since SSH can answer first and systemd-analyze
refuses until it has. In the boot scenario, a non-zero exit from
is-system-running (as for "degraded") no longer ends the script under
set -e before the diagnostics are saved, and a failed query for failed
units writes a marker instead of an empty file that read as "none".
Boots the installed system a second time, records the time to SSH and
systemd-analyze, and asserts systemd reaches running with no failed
units. It gives CI a scenario that passes on today's installer and a
number for every change that touches boot.
Emir Beganovic