basalt-26.3: roachtest: ssh_problem failed

**Note:** This build has runtime assertions enabled. If the same failure was hit in a run without assertions enabled, there should be a similar failure without this message. If there isn't one, then this failure is likely due to an assertion violation or (assertion) timeout.

roachtest.ssh_problem [failed](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_Roachtests_GreenRoachtestNightlyGcePrivateBasaltBazel/21511478?buildTab=log) with [artifacts](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_Roachtests_GreenRoachtestNightlyGcePrivateBasaltBazel/21511478?buildTab=artifacts#/backup-restore/round-trip) on basalt-26.3 @ [9d68ab785115d04ed7ab69c88e35b730f63624e7](https://github.com/cockroachdb/cockroach/commits/9d68ab785115d04ed7ab69c88e35b730f63624e7):

```
test backup-restore/round-trip failed: (test_runner.go:1087).func4: creating Basalt backing cluster teamcity-21511478-1789107039-23-n4cpu4-basalt: not all nodes booted successfully: timed out after 5m: TRANSIENT_ERROR(ssh_problem): exit status 255 [owner=test-eng]
```

Parameters:
- MetamorphicBasaltMultiAZ=false
- cloud=gce
- coverageBuild=false
- cpu=4
- diskCount=0
- runtimeAssertionsBuild=true
- storageNodesVersion=v0.1.19-nightly.20260910
Help

See: [roachtest README](https://github.com/cockroachdb/cockroach/blob/master/pkg/cmd/roachtest/README.md)

See: [How To Investigate \(internal\)](https://cockroachlabs.atlassian.net/l/c/SSSBr8c7)

/cc @cockroachlabs/test-eng

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*ssh_problem.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Start with the roachtest README and test_runner.go:1087, then inspect the TeamCity log and backup-restore/round-trip artifacts for build 21511478. Determine why the Basalt backing cluster hit ssh_problem while booting and verify that the roachtest no longer reports this failure.

Written by the indexing model from the issue text.