Avoid using non-essential frequently-changing command

What does this MR do?

The dataloss command has been changed a few time recently, causing tests to fail that expected the behavior before the change. Most recently: gitaly!2449 (merged)

The dataloss command is not really required in this test to confirm when nodes are inconsistent. The rake 'replicas' task is enough for that. The command was included because it was useful to test that it performs as expected, but the test loses its value when the behavior under test changes so frequently.

This also fixes a problem in PraefectManager.replicated? that caused the retry loop to end prematurely.

Closes #235179 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
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• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
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Security

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