After a partial upgrade, /etc/soversion already reads the target version, so
soup's startup line "Found that Security Onion X is currently installed" made
it look finished even as soup resumed. When a resume marker is present and
differs from the installed version, print an explicit NOTE that the grid is only
partially upgraded and this run will resume and complete it.
Also clear any stale resume marker in the already-latest path so a successfully
completed upgrade is never mistaken for a partial one and re-run on a later
invocation (the marker is normally removed at the end of postupgrade_changes;
this is a belt-and-suspenders guard).
When soup fails via the EXIT trap after it has begun modifying the system, print
a prominent UPGRADE INCOMPLETE banner instructing the user to run soup again to
resume and complete the update. Gated on a new SOUP_UPGRADE_STARTED flag set at
the start of the hotfix and upgrade branches, so pre-flight gate failures (ES
compatibility, disk, network) that abort before any changes are made do not show
it.
A failed highstate mid-upgrade left /etc/soversion already advanced to the
target version (the highstate stamps it from the pillar via the soversionfile
state), so a re-run of soup saw INSTALLEDVERSION == NEWVERSION and reported
"already running the latest version", stranding the box with post-upgrade
steps never run.
Introduce /etc/sopostversion, a soup-owned marker (no salt state manages it)
that records post-upgrade walk progress. It is seeded from the pre-upgrade
version before the highstate, advanced after each post_to_* step, and removed
on successful completion. upgrade_check treats a leftover marker as "upgrade
not finished" and resumes the remaining post steps instead of bailing.
Also fix the hotfix path: /etc/sohotfix was written before the hotfix
highstate, so a failed hotfix highstate looked already-applied on re-run.
Since no salt state manages /etc/sohotfix, defer its write (update_version)
until after the highstate succeeds so it is an honest completion marker.