[ML] Correctly print job state when delete job fails (elastic/x-pack-elasticsearch#1310)

relates elastic/x-pack-elasticsearch#1307

Original commit: elastic/x-pack-elasticsearch@25fb18ed0b

plugin/src/main/java/org/elasticsearch/xpack/ml/MlMetadata.java

@@ -362,7 +362,7 @@ public class MlMetadata implements MetaData.Custom {
             PersistentTask<?> jobTask = getJobTask(jobId, tasks);
             if (jobTask != null) {
                 throw ExceptionsHelper.conflictStatusException("Cannot delete job [" + jobId + "] because the job is "
-                        + jobTask.getStatus());
+                        + ((JobTaskStatus) jobTask.getStatus()).getState());
             }
             Job.Builder jobBuilder = new Job.Builder(job);
             jobBuilder.setDeleted(true);

plugin/src/main/java/org/elasticsearch/xpack/ml/action/OpenJobAction.java

@@ -466,7 +466,7 @@ public class OpenJobAction extends Action<OpenJobAction.Request, OpenJobAction.R
                     case FAILED:
                         return true;
                     default:
-                        throw new IllegalStateException("Unexpected job state [" + jobState + "]");
+                        throw new IllegalStateException("Unexpected job state [" + jobState.getState() + "]");
 
                 }
             }

plugin/src/test/resources/rest-api-spec/test/ml/jobs_crud.yaml

@@ -296,6 +296,34 @@
       catch: /Cannot delete job \[jobs-crud-datafeed-job\] because datafeed \[jobs-crud-test-datafeed-1\] refers to it/
       xpack.ml.delete_job:
         job_id: jobs-crud-datafeed-job
+
+---
+"Test delete job that is opened":
+  - do:
+      xpack.ml.put_job:
+        job_id: delete-opened-job
+        body:  >
+          {
+            "analysis_config" : {
+                "bucket_span": "1h",
+                "detectors" :[{"function":"count"}]
+            },
+            "data_description" : {
+                "time_field":"time"
+            }
+          }
+  - match: { job_id: "delete-opened-job" }
+
+  - do:
+      xpack.ml.open_job:
+        job_id: delete-opened-job
+  - match: { opened: true }
+
+  - do:
+      catch: /Cannot delete job \[delete-opened-job\] because the job is opened/
+      xpack.ml.delete_job:
+        job_id: delete-opened-job
+
 ---
 "Test close job":