Attempting to work around random failure.
https://jenkins.ci.cloudbees.com/job/core/job/acceptance-test-harness/409/testReport/plugins/NodeLabelParameterPluginTest/run_on_a_particular_offline_slave_with_ignore/
org.openqa.selenium.UnhandledAlertException: Modal dialog present: This page is asking you to confirm that you want to leave - data you have entered may not be saved.
…
	at …
	at org.jenkinsci.test.acceptance.slave.LocalSlaveController.install(LocalSlaveController.java:21)
	at plugins.NodeLabelParameterPluginTest.run_on_a_particular_offline_slave_with_ignore(NodeLabelParameterPluginTest.java:223)
suggesting that the message is coming from the unsaved configuration page of the new job.
(The dialog _should_ be shown only if you have changed something, which normally you would not have.
But apparently once in a while it is shown anyway?)