release-21.2: roachtest: harden the sqlsmith test

[blathers-crl]

Backport 1/1 commits from #70280 on behalf of @yuzefovich.

/cc @cockroachdb/release

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Previously, we had some false positives from the sqlsmith roachtest
filed because of "inbox communication errors" which were actually
triggered because of the vectorized panic injection. These errors
usually mean that a node died, so we used the errors as a proxy for the
crash. This commit adjusts the test to instead ping all nodes in the
cluster to see whether they are up or not and not rely on the
communication errors. This allows us to ignore the false positives
because of the panic injection.

Fixes: #66174.

Release note: None

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Release justification:

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[rytaft]

Hold off on merging for now.

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @yuzefovich)

[yuzefovich]

Yeah, I'll wait until 21.2.0 is out - plus I want to see that this change on master fixes those false positives for good.

[yuzefovich]

@rytaft I think this change does fix the false positive issue, so I'm thinking whether we should go ahead and merge this given it is a testing only change to reduce the noise?

[rytaft]

Yep, go ahead and merge. Thanks!