Added SemaphoreStep.waitForStart() for workflow to wait until semapho…

…re release before continuing

src/test/java/com/cloudbees/jenkins/support/impl/NodeExecutorsTest.java

@@ -173,7 +173,7 @@ public void addContentsFiltered() throws Exception {
         WorkflowRun workflowRun = Optional.ofNullable(p.scheduleBuild2(0))
                 .orElseThrow(AssertionFailedError::new)
                 .waitForStart();
-        j.waitForMessage("Running on", workflowRun);
+        SemaphoreStep.waitForStart("wait/1", workflowRun);
 
         ContentFilter filter = SupportPlugin.getDefaultContentFilter();