test(ingestor): TestStatsFileHasNoCredentials_118 flakes when a stats number contains '1234'

[dborup]

Problem

TestStatsFileHasNoCredentials_118 in cmd/ingestor/mqtt_status_credentials_118_test.go fails intermittently:

mqtt_status_credentials_118_test.go:222: stats file leaks "1234": {"sampledAt":"...", ...}

secretParts118 includes very short numeric "secrets" ("1234", "2024") and "abc". The test then asserts that none of them occurs anywhere in the whole stats-file JSON. That JSON contains timestamps, Unix times, counters and byte sizes, so any number that happens to contain 1234 fails the test, even though no credential leaked. It was seen on PR #246, a server-only change.

Proposed fix

• Use secret test values that cannot occur by chance in numbers or timestamps, e.g. zq1234zq and pw2024pw, in the broker URLs and in secretParts118. Keep the coverage: masked user, password, query and fragment parts.
• Optionally, assert only on the string fields that can carry broker text (error texts, broker labels) instead of the whole JSON blob.

Acceptance

• The test still fails if masking is removed (mutant: errForLog returns the raw error).
• It no longer depends on numeric content. Prove it with a run that injects a counter or timestamp containing 1234, or with -count=200.

[dborup]

Fixed by #253 (merged as 0572e7f9).