accounts::tests::test_migrate_account fails due to "auto_vacuum"

[link2xt]

Since commit 7d2cca8 running

while cargo test migrate -- --nocapture; do :; done

results in errors such as

running 1 test
thread 'accounts::tests::test_migrate_account' panicked at 'called `Option::unwrap()` on a `None` value', src/accounts.rs:624:18
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
test accounts::tests::test_migrate_account ... FAILED

failures:

failures:
    accounts::tests::test_migrate_account

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 646 filtered out; finished in 0.46s

[r10s]

i can confirm that. moreover, cargo test is much slower, >1 minute instead of <10 seconds on my machine, maybe related, i filed #4051 for that.

[link2xt]

Fixed by #4053