The Proxmox-side LXC Docker inventory script masked `docker ps`
failures with `|| true`, so when `pct exec` was truncated, slow, or
`docker ps` itself transiently failed, the parser produced an
ok=true report with `containers=[]` and `ApplyDockerReport` blanked
the host's container list. Containers then reappeared on the next
successful poll, producing the visible flicker on the Docker page.
Emit a `PS_OK` marker only when `docker ps` exits cleanly, and
refuse to apply the report when the marker is absent. A genuine
"host has zero containers" state still applies (PS_OK present,
zero CONTAINER lines), but a truncated or failed poll now skips
apply and lets the previous container list survive the inter-poll
gap. Add regression tests for both paths.
rcourtman
fc72e3d8d1