remove unknown from failure states (#125)

Author: adwk67

stacks/airflow/airflow.yaml

@@ -142,7 +142,9 @@ data:
 
     class SparkKubernetesSensor(BaseSensorOperator):
         template_fields = ("application_name", "namespace")
-        FAILURE_STATES = ("Failed", "Unknown")
+        # See https://github.com/stackabletech/spark-k8s-operator/pull/460/files#diff-d737837121132af6b60f50279a78464b05dcfd06c05d1d090f4198a5e962b5f6R371
+        # Unknown is set immediately so it must be excluded from the failed states.
+        FAILURE_STATES = ("Failed")
         SUCCESS_STATES = ("Succeeded")
 
         def __init__(