Flaky test failure in va:TestPreresolvedDialerTimeout

[aarongable]

I've seen this failure several times when running unit tests locally, but it always goes away after a re-run:

--- FAIL: TestPreresolvedDialerTimeout (0.00s)
    http_test.go:97: fetch returned before 50ms (took: 4.459074ms) with va.ipError{ip:net.IP{0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xff, 0xff, 0xc6, 0x33, 0x64, 0x1}, err:(*url.Error)(0xc00056be00)}
2024/03/06 23:01:12 http: TLS handshake error from 127.0.0.1:36520: EOF
2024/03/06 23:01:12 http: TLS handshake error from 127.0.0.1:45954: tls: client requested unsupported application protocols ([acme-tls/1])
2024/03/06 23:01:12 http: TLS handshake error from 127.0.0.1:57118: tls: client requested unsupported application protocols ([acme-tls/1])
2024/03/06 23:01:12 http: TLS handshake error from 127.0.0.1:38132: tls: client requested unsupported application protocols ([acme-tls/1])
2024/03/06 23:01:12 http: TLS handshake error from 127.0.0.1:44642: tls: client offered only unsupported versions: [304 303]
2024/03/06 23:01:12 http: TLS handshake error from 127.0.0.1:48248: remote error: tls: bad certificate
2024/03/06 23:01:12 http: TLS handshake error from 127.0.0.1:34180: remote error: tls: bad certificate
FAIL
FAIL    github.com/letsencrypt/boulder/va       1.458s
FAIL

It sometimes affects other tests such as TestHTTPDialTimeout.