test failure in CI: integration_tests::updates::test_update_end_to_end

In the CI run for the putback of https://github.com/oxidecomputer/omicron/commit/44b326b9ab89a842df3d84fa5ac15b31eeabb9e5 (#1547) we saw a failure in the integration_tests::unauthorized::test_unauthorized test.

You can see the failure in the buildomat output for the run: https://buildomat.eng.oxide.computer/wg/0/details/01G9QKYAH8NX1V84S5CWD89877/VlQvoPXBlhK3a2vS6HJvwiUPrugKP6GBqF8ApnXZM1ORBL1l/01G9QKYKQ7F5GQEE612EZCPT6C#S3971

3971 | 2022-08-05T19:15:09.796Z | test integration_tests::unauthorized::test_unauthorized has been running for over 60 seconds
-- | -- | --
3972 | 2022-08-05T19:15:44.287Z | test integration_tests::unauthorized::test_unauthorized ... ok
3973 | 2022-08-05T19:15:44.297Z |  
3974 | 2022-08-05T19:15:44.303Z | failures:
3975 | 2022-08-05T19:15:44.310Z |  
3976 | 2022-08-05T19:15:44.316Z | ---- integration_tests::updates::test_update_end_to_end stdout ----
3977 | 2022-08-05T19:15:44.323Z | log file: "/var/tmp/omicron_tmp/test_all-c3586aa52ca27013-test_update_end_to_end.5320.109.log"
3978 | 2022-08-05T19:15:44.328Z | note: configured to log to "/var/tmp/omicron_tmp/test_all-c3586aa52ca27013-test_update_end_to_end.5320.109.log"
3979 | 2022-08-05T19:15:44.334Z | log file: "/var/tmp/omicron_tmp/test_all-c3586aa52ca27013-test_update_end_to_end.5320.110.log"
3980 | 2022-08-05T19:15:44.341Z | note: configured to log to "/var/tmp/omicron_tmp/test_all-c3586aa52ca27013-test_update_end_to_end.5320.110.log"
3981 | 2022-08-05T19:15:44.351Z | thread 'integration_tests::updates::test_update_end_to_end' panicked at 'assertion failed: `(left == right)`
3982 | 2022-08-05T19:15:44.357Z | left: `[]`,
3983 | 2022-08-05T19:15:44.366Z | right: `[104, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100]`', nexus/tests/integration_tests/updates.rs:95:5
3984 | 2022-08-05T19:15:44.373Z | note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
3985 | 2022-08-05T19:15:44.380Z | WARN: dropped CockroachInstance without cleaning it up first (there may still be a child process running and a temporary directory leaked)
3986 | 2022-08-05T19:15:44.387Z | WARN: temporary directory leaked: /var/tmp/omicron_tmp/.tmpvMSlTa
3987 | 2022-08-05T19:15:44.441Z | WARN: dropped ClickHouseInstance without cleaning it up first (there may still be a child process running and a temporary directory leaked)
3988 | 2022-08-05T19:15:44.449Z |  
3989 | 2022-08-05T19:15:44.456Z |  
3990 | 2022-08-05T19:15:44.463Z | failures:
3991 | 2022-08-05T19:15:44.469Z | integration_tests::updates::test_update_end_to_end
3992 | 2022-08-05T19:15:44.474Z |  
3993 | 2022-08-05T19:15:44.480Z | test result: FAILED. 130 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 287.97s

Several log files were preserved, and you can see raw and rendered versions in the job:

https://buildomat.eng.oxide.computer/wg/0/details/01G9QKYAH8NX1V84S5CWD89877/VlQvoPXBlhK3a2vS6HJvwiUPrugKP6GBqF8ApnXZM1ORBL1l/01G9QKYKQ7F5GQEE612EZCPT6C

Start with nexus/tests/integration_tests/updates.rs around line 95 and inspect the preserved raw and rendered Buildomat logs linked in the issue. Reproduce integration_tests::updates::test_update_end_to_end and trace why the assertion returns an empty value instead of “hello world”; done means the test passes reliably in CI.