Three follow-ups to argus's review of #5237:
- A down secondary's retry runs `restore` under RESTORE_TIMEOUT (2 min).
Tries run one per tick on one future, so a restore that never resolved
held back every other down account's retries for good; a try that
outlasts the timeout now counts as a failure like any other.
- `client::build_and_restore` warns about a rejected token only for the
primary, which exits right after. For a secondary it logs at debug: the
retry loop already warns once per outage (`DownAccounts::failed` is news
on the first failure and on a changed reason, and an account that came
up starts afresh), so the extra warn repeated on every try.
- `a_secondary_that_comes_up_late_does_not_wipe_the_todos` runs the late
bring-up in a child process of the test binary with HIVE_AGENT_SOCKET
pointed at the test's listener. In-process the variable was unset, so a
wipe placed back in the bring-up path was a no-op and the test passed.
New tests: a_second_rejection_in_a_row_does_not_warn_again (captured logs, alone
in a child process since tracing caches callsite interest process-wide;
a stub whoami answering M_UNKNOWN_TOKEN, the real build_and_restore),
a_failure_after_the_account_came_up_is_news_again, and
an_account_whose_restore_hangs_does_not_hold_back_the_others (paused time).
7b1435eaea