ServiceEntryPointBenchmarkFixture::doRequest only checks the transport Status and discards the reply body. Command failures (parse errors, execution errors) come back as ok: 0, so a broken benchmark will be reporting numbers for the error path. This happened before with BM_INSERT (it was silently failing, see PERF-8454).

In doRequest, we should parse the reply and iassert that ok is truthy, including the reply body in the failure message. Deliberately do not fail on writeErrors inside an ok: 1 reply (the fixtures rely on tolerated duplicate-key write errors during repopulation (e.g. _populateTestData racing across 16 threads).