[JENKINS-57965] Prevent save of KubernetesSlave through UI

[Vlatombe]

No description provided.

[jglick]

Not sure if test timeouts are flakes or not. I did notice this which might be related:

java.lang.NullPointerException
	at hudson.model.Node.toComputer(Node.java:208)
	at hudson.model.Slave.getComputer(Slave.java:539)
	at org.csanchez.jenkins.plugins.kubernetes.KubernetesLauncher.launch(KubernetesLauncher.java:144)
	at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:294)
	at …

[Vlatombe]

I looked at the failure, and what I understood is the following:

• Jenkins is being shut down
• The Kubernetes launcher was still running and throws a NPE because Jenkins singleton is now null. Ideally we'd need to interrupt the launcher thread upon shutdown?
• The timeout seems to be caused by a serie of remoting calls which execute serially (each thread is trying to lock the Queue), and the one holding the lock is waiting on a remoting call.

[jglick]

If you want to write a functional test for it, use

• JenkinsRule.createDummySecurityRealm + MockAuthorizationStrategy (actually not even necessary since you are denying permission even to admins)
• JenkinsRule.WebClient.goTo or similar overloads

[jglick]

nonstandard formatting these three lines, FYI