getDockerCommandPayload returned dispatched commands on every report
fetch, causing the agent to re-execute check-updates on every poll
cycle. When the ack also failed, the report was buffered and retried,
creating an infinite loop.
- Only return command payload on the queued->dispatched transition;
subsequent fetches return nil (agent already received it).
- Don't propagate ack errors from handleCheckUpdatesCommand; the report
was delivered and check-updates is fire-and-forget. Command expires
if ack never succeeds.
Refs #1504
rcourtman
d6aed650b1