Fix ignore_unstable flag

Related-prod: PRODX-18117
Change-Id: I46b13f08869ac5a9ede9752147934335d1f275f3
diff --git a/src/com/mirantis/mk/Workflow.groovy b/src/com/mirantis/mk/Workflow.groovy
index fc1374d..03a43a6 100644
--- a/src/com/mirantis/mk/Workflow.groovy
+++ b/src/com/mirantis/mk/Workflow.groovy
@@ -410,7 +410,7 @@
                         ignoreStepResult = step['ignore_not_built'] ?: false
                         break;
                     case "UNSTABLE":
-                        ignoreStepResult = step['ignore_unstable'] ?: false
+                        ignoreStepResult = step['ignore_unstable'] ?: (step['ignore_failed'] ?: false)
                         break;
                     default:
                         ignoreStepResult = step['ignore_failed'] ?: false