Do not block on FutureImpl.

After jenkinsci/workflow-step-api-plugin#73 this caused `SecretsMasker` to block on a `KubernetesComputer`
which in turn blocked provisioning of a `TaskListener`, causing `RestartPipelineTest.terminatedPodAfterRestart` to fail to find a message:

```
FINE	o.j.p.w.s.d.DurableTaskStep$Execution#getWorkspace: rediscovering that terminated-pod-after-restart-1-8fb2m-j206k-8x125 has been removed and timeout has expired
FINE	o.j.p.w.s.d.DurableTaskStep$Execution#_listener: JENKINS-34021: could not get TaskListener in CpsStepContext[9:sh]:Owner[terminated Pod After Restart/1:terminated Pod After Restart jenkinsci#1]
java.util.concurrent.TimeoutException
	at hudson.remoting.AsyncFutureImpl.get(AsyncFutureImpl.java:102)
	at org.jenkinsci.plugins.workflow.support.steps.ExecutorStepDynamicContext$Translator.get(ExecutorStepDynamicContext.java:115)
Caused: java.io.IOException
	at org.jenkinsci.plugins.workflow.support.steps.ExecutorStepDynamicContext$Translator.get(ExecutorStepDynamicContext.java:118)
	at org.jenkinsci.plugins.workflow.steps.DynamicContext$Typed.get(DynamicContext.java:97)
	at org.jenkinsci.plugins.workflow.cps.ContextVariableSet.get(ContextVariableSet.java:139)
	at org.jenkinsci.plugins.workflow.cps.ContextVariableSet$1Delegate.doGet(ContextVariableSet.java:98)
	at org.jenkinsci.plugins.workflow.support.DefaultStepContext.get(DefaultStepContext.java:75)
	at org.csanchez.jenkins.plugins.kubernetes.pipeline.SecretsMasker$Factory.get(SecretsMasker.java:85)
	at org.csanchez.jenkins.plugins.kubernetes.pipeline.SecretsMasker$Factory.get(SecretsMasker.java:73)
	at org.jenkinsci.plugins.workflow.steps.DynamicContext$Typed.get(DynamicContext.java:95)
	at org.jenkinsci.plugins.workflow.cps.ContextVariableSet.get(ContextVariableSet.java:139)
	at org.jenkinsci.plugins.workflow.cps.CpsThread.getContextVariable(CpsThread.java:135)
	at org.jenkinsci.plugins.workflow.cps.CpsStepContext.doGet(CpsStepContext.java:297)
	at org.jenkinsci.plugins.workflow.support.DefaultStepContext.get(DefaultStepContext.java:75)
	at org.jenkinsci.plugins.workflow.support.DefaultStepContext.getListener(DefaultStepContext.java:127)
	at org.jenkinsci.plugins.workflow.support.DefaultStepContext.get(DefaultStepContext.java:87)
	at org.jenkinsci.plugins.workflow.steps.durable_task.DurableTaskStep$Execution._listener(DurableTaskStep.java:421)
	at org.jenkinsci.plugins.workflow.steps.durable_task.DurableTaskStep$Execution.listener(DurableTaskStep.java:412)
	at org.jenkinsci.plugins.workflow.steps.durable_task.DurableTaskStep$Execution.getWorkspace(DurableTaskStep.java:363)
	at org.jenkinsci.plugins.workflow.steps.durable_task.DurableTaskStep$Execution.check(DurableTaskStep.java:570)
	at org.jenkinsci.plugins.workflow.steps.durable_task.DurableTaskStep$Execution.run(DurableTaskStep.java:553)
	at …
FINE	o.j.p.w.s.d.DurableTaskStep$Execution$NewlineSafeTaskListener#getLogger: creating filtered stream
FINE	o.j.p.w.s.d.DurableTaskStep$Execution#_listener: terminated-pod-after-restart-1-8fb2m-j206k-8x125 has been removed for 15 sec, assuming it is not coming back
```

src/main/java/org/jenkinsci/plugins/workflow/support/steps/ExecutorStepDynamicContext.java

@@ -105,11 +105,14 @@ private static abstract class Translator<T> extends DynamicContext.Typed<T> {
                 if (c.future == null) {
                     throw new IOException("Attempt to look up context from ExecutorStepExecution which has not been resumed");
                 }
+                if (!c.future.isDone()) {
+                    LOGGER.fine(() -> "queue item has not been scheduled for " + c.path + " on " + c.node + ", declining to provide any " + type().getSimpleName());
+                    return null;
+                }
                 LOGGER.fine(() -> "waiting for queue item to be scheduled for " + c.path + " on " + c.node);
                 Queue.Executable exec;
                 try {
-                    // TODO block here, or just return null? DurableTaskStep.Execution.getWorkspace will tolerate nulls, but if there are any other resumable steps expecting a workspace, they could fail
-                    exec = c.future.get(ExecutorStepExecution.TIMEOUT_WAITING_FOR_NODE_MILLIS, TimeUnit.MILLISECONDS);
+                    exec = c.future.get(1, TimeUnit.SECONDS);
                 } catch (ExecutionException | TimeoutException | CancellationException x) {
                     c.future = Futures.immediateFailedFuture(x);
                     throw new IOException(x);