acceptance: TestDockerCLI/test_demo_node_cmds.tcl flaked [index out of range [6] with length 6]

[rafiss]

Observed here: https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_BazelEssentialCi/8664061?showRootCauses=false&expandBuildChangesSection=true&expandBuildProblemsSection=true&expandBuildTestsSection=true

Maybe relates to #96450 and #96239 and #96162

Relevant logs:

expect: does "\r\nroot@127.0.0.1:26257/defaultdb> " (spawn_id exp3) match glob pattern "defaultdb>"? yes
expect: set expect_out(0,string) "defaultdb>"
expect: set expect_out(spawn_id) "exp3"
expect: set expect_out(buffer) "\r\nroot@127.0.0.1:26257/defaultdb>"
send: sending "\demo add region=ca-central,zone=a\r" to { exp3 }

expect: does " " (spawn_id exp3) match glob pattern "node 6 has been added with locality "region=ca-central,zone=a""? no
root@127.0.0.1:26257/defaultdb> \demo add region=ca-central,zone=a

expect: does " \demo add region=ca-central,zone=a\r\n" (spawn_id exp3) match glob pattern "node 6 has been added with locality "region=ca-central,zone=a""? no
*
* ERROR: a panic has occurred!
* runtime error: index out of range [6] with length 6
* (1) attached stack trace
*   -- stack trace:
*   | runtime.gopanic
*   | 	GOROOT/src/runtime/panic.go:890
*   | runtime.goPanicIndex
*   | 	GOROOT/src/runtime/panic.go:113
*   | github.com/cockroachdb/cockroach/pkg/cli/democluster.(*transientCluster).GetLocality
*   | 	github.com/cockroachdb/cockroach/pkg/cli/democluster/demo_cluster.go:1858
*   | github.com/cockroachdb/cockroach/pkg/cli/clisqlshell.(*cliState).handleDemoAddNode
*   | 	github.com/cockroachdb/cockroach/pkg/cli/clisqlshell/sql.go:682
*   | github.com/cockroachdb/cockroach/pkg/cli/clisqlshell.(*cliState).handleDemo
*   | 	github.com/cockroachdb/cockroach/pkg/cli/clisqlshell/sql.go:664
*   | github.com/cockroachdb/cockroach/pkg/cli/clisqlshell.(*cliState).doHandleCliCmd
*   | 	github.com/cockroachdb/cockroach/pkg/cli/clisqlshell/sql.go:1442
*   | github.com/cockroachdb/cockroach/pkg/cli/clisqlshell.(*cliState).doRunShell
*   | 	github.com/cockroachdb/cockroach/pkg/cli/clisqlshell/sql.go:2157
*   | github.com/cockroachdb/cockroach/pkg/cli/clisqlshell.(*cliState).RunInteractive
*   | 	github.com/cockroachdb/cockroach/pkg/cli/clisqlshell/sql.go:2106
*   | github.com/cockroachdb/cockroach/pkg/cli/clisqlcfg.(*Context).Run
*   | 	github.com/cockroachdb/cockroach/pkg/cli/clisqlcfg/context.go:225
*   | github.com/cockroachdb/cockroach/pkg/cli.runDemoInternal
*   | 	github.com/cockroachdb/cockroach/pkg/cli/demo.go:381
*   | github.com/cockroachdb/cockroach/pkg/cli.runDemo

Jira issue: CRDB-24444

[rafiss]

closing in favor of #102257