soft fail cluster tests for data gathering

Created by: davejrt

These tests have been historically flaky, between infra and the tests themselves.

https://github.com/sourcegraph/sourcegraph/issues/25977 https://github.com/sourcegraph/sourcegraph/issues/31342

It's been challenging to gather enough accurate data so the intent here is to add a soft fail so we can get as many attempts as possible to see if there are any patterns we can observe.

Test plan

a test run here forcing the exit code to make soft fail is working https://buildkite.com/sourcegraph/sourcegraph/builds/133725#5c966b24-2a16-4b30-a1ac-7628e4cf0312