Apply suggestions from code review

Co-authored-by: Jesse Glick <[email protected]>

Author: Vlatombe

src/test/resources/org/csanchez/jenkins/plugins/kubernetes/pipeline/invalidImageGetsCancelled.groovy

@@ -5,6 +5,6 @@ spec:
     image: some/invalid
 ''') {
   node(POD_LABEL) {
-    sh 'This will never run'
+    sh 'false "This will never run"'
   }
 }