[JENKINS-72441] Prevent lock contention on KubernetesLauncher#isLaunchSupported

[Dohbedoh]

JENKINS-72441

As per #1392 (comment)

Remove the synchronized - that was added to fix a spotbug warning - causing lock contention on accessors. And use an AtomicBoolean instead to make spotbugs happy.

Testing done

Testing agent low to launch

• Create a pipeline:

pipeline {
    agent none
    stages {
        stage('Hello') {
            steps {
                podTemplate(envVars: [envVar(key: 'JENKINS_TUNNEL', value: ':50999')]) {
                    node(POD_LABEL) {
                        // some block
                        sh "echo 'Hello World'"
                    }
                }
            }
        }
    }
}

• Run it
• Follow the link to the agent created from the console out
• Validate that the agent page is accessible

Testing normal launch

• Create a pipeline:

pipeline {
    agent none
    stages {
        stage('Hello') {
            steps {
                podTemplate {
                    node(POD_LABEL) {
                        // some block
                        sh "echo 'Hello World'"
                    }
                }
            }
        }
    }
}

• Run it
• Follow the link to the agent created from the console out
• Validate that the agent page is accessible and that the build completes

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6. Ensure you have provided tests - that demonstrates feature works or fixes the issue

[jglick]

This is not OK—the field is not transient so it would be persisted in the XStream form of the node config. Granted these agents are usually ephemeral, but they do survive controller restarts and plugin upgrades.

I would suggest restoring it to boolean and just make it volatile to shut up SpotBugs.

[jglick]

What does this have to do with https://issues.jenkins.io/browse/JENKINS-72441 in artifact-manager-s3? Mistyped issue number?