Deleting a couple of TODO comments already covered by open cards.
Check for new output (or exit) from a durable task at frequent intervals, backing off if quiet.
https://trello.com/c/RKRzJIAt/110-durabletaskstep-checker-replacement
Trying to avoid an unreproducible failure in WorkflowTest.demo.
java.util.concurrent.ExecutionException
	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
	at java.util.concurrent.FutureTask.get(FutureTask.java:188)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$3.get(CpsThreadGroup.java:230)
	at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.waitForSuspension(CpsFlowExecution.java:502)
	at org.jenkinsci.plugins.workflow.SingleJobTestBase.waitForWorkflowToSuspend(SingleJobTestBase.java:108)
	at org.jenkinsci.plugins.workflow.SingleJobTestBase.waitForWorkflowToComplete(SingleJobTestBase.java:95)
	at org.jenkinsci.plugins.workflow.WorkflowTest$2.evaluate(WorkflowTest.java:111)
	at org.jvnet.hudson.test.RestartableJenkinsRule$3.evaluate(RestartableJenkinsRule.java:84)
	at org.jvnet.hudson.test.JenkinsRule$2.evaluate(JenkinsRule.java:486)
	at org.jvnet.hudson.test.RestartableJenkinsRule.run(RestartableJenkinsRule.java:100)
	at org.jvnet.hudson.test.RestartableJenkinsRule.access$100(RestartableJenkinsRule.java:30)
	at org.jvnet.hudson.test.RestartableJenkinsRule$1.evaluate(RestartableJenkinsRule.java:64)
	at …
Caused by: java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.FutureTask@17917e5d rejected from java.util.concurrent.ThreadPoolExecutor@50ff17c1[Shutting down, pool size = 1, active threads = 1, queued tasks = 0, completed tasks = 7]
	at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2048)
	at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:821)
	at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1372)
	at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:110)
	at java.util.concurrent.Executors$DelegatedExecutorService.submit(Executors.java:638)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:174)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:166)
	at java.util.concurrent.FutureTask.run(FutureTask.java:262)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:745)
	at org.jenkinsci.plugins.workflow.cps.CpsVmThread.run(CpsVmThread.java:21)
Adapted to changes in DurableTaskStep.
The invoking job should be specified via @StepContextParameter so our descriptor declares that it is needed.
More realistic test of build triggers across folders.
No reason to be a RunAction2 if we do not do anything when attached.
And can use InvisibleAction as a convenience.
Added UpstreamCause.
Trying to block random failures in WorkflowTest.authenticate.
durable-task 0.7 to pick up reworked JENKINS-22249 fix.