Intermittent failure in TestCertificateDNSUpdated

[Joseph Phillips]

As seen here:
https://jenkins.juju.canonical.com/job/github-make-check-juju/9747

This look like it might be related to recent worker changes around restarting when agents detect that they should be controllers.

The dependency engine starts up, then immediately shuts everything down.

14:44:21 // Start the agent.
14:44:21 go func() { c.Check(a.Run(cmdtesting.Context(c)), jc.ErrorIsNil) }()
14:44:21 ... value *errors.Err = &errors.unformatter{message:"agent should be restarted", cause:error(nil), previous:error(nil), function:"github.com/juju/juju/worker.init", line:20} ("agent should be restarted")
14:44:21 ... error stack:
14:44:21 github.com/juju/juju/worker.init:20: agent should be restarted