release-26.2.6-rc: roachtest: ssh_problem failed

roachtest.ssh_problem [failed](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_Roachtests_VectorIndexingRoachtestNightlyGceBazel/21461716?buildTab=log) with [artifacts](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_Roachtests_VectorIndexingRoachtestNightlyGceBazel/21461716?buildTab=artifacts#/vecindex/random-s/nodes=1/prefix=0) on release-26.2.6-rc @ [c27a8acb37fbc2e0e191decd9b433e27f13b96fb](https://github.com/cockroachdb/cockroach/commits/c27a8acb37fbc2e0e191decd9b433e27f13b96fb):

```
test vecindex/random-s/nodes=1/prefix=0 failed: (test_runner.go:1017).func4: not all nodes booted successfully: timed out after 5m: TRANSIENT_ERROR(ssh_problem): exit status 255 [owner=test-eng]
```

Parameters:
- cloud=gce
- coverageBuild=false
- cpu=4
- diskCount=0
- runtimeAssertionsBuild=false
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)

Same failure on other branches

- #173320 basalt-26.3: roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-basalt-26.3]
- #173321 basalt-26.3: roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-basalt-26.3]
- #173249 release-26.3.1-rc: roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-26.3.1-rc]
- #172584 release-26.3.0-rc: roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-26.3.0-rc]
- #172557 roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-25.4.14-rc]
- #172517 roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-25.2.22-rc]
- #172515 roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-26.1.8-rc]
- #172513 release-26.2.5-rc: roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-26.2.5-rc]
- #172364 release-26.3: roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-26.3]
- #172363 roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-master]

/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)

Jira issue: CRDB-66643

Start with the roachtest README and the failure at test_runner.go:1017, then inspect the linked TeamCity log and artifacts for the ssh_problem details. Compare the repeated cross-branch failures listed in the issue and the roachdash results. Done means identifying the cause of the SSH startup failure and confirming the affected roachtest no longer fails for that reason.

Written by the indexing model from the issue text.