roachtest: schemachange/database-version-upgrade failed

[cockroach-teamcity]

roachtest.schemachange/database-version-upgrade failed with artifacts on release-21.2 @ 37dee546a7c52870a8dc58826f0cffe2afa8d47a:

The test failed on branch=release-21.2, cloud=gce:
test artifacts and logs in: /home/agent/work/.go/src/github.com/cockroachdb/cockroach/artifacts/schemachange/database-version-upgrade/run_1
    cluster.go:1296,context.go:89,cluster.go:1284,test_runner.go:866: dead node detection: /home/agent/work/.go/src/github.com/cockroachdb/cockroach/bin/roachprod monitor teamcity-4531448-1646810149-21-n3cpu4 --oneshot --ignore-empty-nodes: exit status 1 3: error: exit status 255
        2: 44216
        1: 59949
        Error: UNCLASSIFIED_PROBLEM: 3: error: exit status 255
        (1) UNCLASSIFIED_PROBLEM
        Wraps: (2) attached stack trace
          -- stack trace:
          | github.com/cockroachdb/cockroach/pkg/roachprod.Monitor
          |     /home/agent/work/.go/src/github.com/cockroachdb/cockroach/pkg/roachprod/roachprod.go:596
          | main.glob..func14
          |     /home/agent/work/.go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:569
          | main.wrap.func1
          |     /home/agent/work/.go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:123
          | github.com/spf13/cobra.(*Command).execute
          |     /home/agent/work/.go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:856
          | github.com/spf13/cobra.(*Command).ExecuteC
          |     /home/agent/work/.go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:960
          | github.com/spf13/cobra.(*Command).Execute
          |     /home/agent/work/.go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:897
          | main.main
          |     /home/agent/work/.go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:1170
          | runtime.main
          |     /usr/local/go/src/runtime/proc.go:255
          | runtime.goexit
          |     /usr/local/go/src/runtime/asm_amd64.s:1581
        Wraps: (3) 3: error: exit status 255
        Error types: (1) errors.Unclassified (2) *withstack.withStack (3) *errutil.leafError

Reproduce

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

/cc @cockroachdb/sql-schema

This test on roachdash | Improve this report!

Jira issue: CRDB-13639

[ajwerner]

This one is odd. The test thinks it finished successfully, but then roachprod infra says the node died, but then by the time we fetch a debug zip after thinking the process died, it was still alive. I'm calling this an infra flake of unknown origin.