Comment 2 for bug 1918680

See here:
https://pastebin.ubuntu.com/p/YPqrVzrgwB/

When the migration-inactive-flag drops, a graceful shut-down should ensue.

Instead, we are throwing an error, changing the status to "failed" as seen here:
https://pastebin.ubuntu.com/p/d7XSfmQycN/

This means the QUIESC stage fails and the migration is aborted.

Fixing this will mean that we don't have to keep retrying migrations until we get lucky and pass the first validation step.