The folder-list cache from #1132 published a reused list only when it
was freshly fetched. When the Pro folder tree had loaded a login first,
the unified build reused that list and never stored it under the
login's JMAP id, so trash and archive for that login's mail were
resolved against the active login's folders until it pushed a change.
A reused list now fills any key nothing has published yet, without
overwriting a live one.
The Pro folder tree also marked a login as loaded before its first
fetch finished and never retried a failure, which left that login's
tree empty until an account switch. A failed load is now retried on
the next run, as the identities hook already does.
Linus Rath
770fb2c84a