Cleanup plugin links upon a cluster reset

Currently plugin links survive cluster reset and there is no way to get
rid of them. Cluster reset seems like a reasonable place to get rid of
them.

Change-Id: Id88c54b34a162881c6662ee1acb6090d4fee3fae
Closes-Bug: #1578700

nailgun/nailgun/objects/cluster_plugin_link.py

@@ -42,3 +42,7 @@ class ClusterPluginLinkCollection(NailgunCollection):
     def create_with_cluster_id(cls, data, cluster_id):
         data['cluster_id'] = cluster_id
         return cls.create(data)
+
+    @classmethod
+    def delete_by_cluster_id(cls, cluster_id):
+        cls.filter_by(None, cluster_id=cluster_id).delete()

nailgun/nailgun/task/manager.py

@@ -919,6 +919,9 @@ class ResetEnvironmentTaskManager(TaskManager):
         for node in nodes:
             objects.Node.reset_vms_created_state(node)
 
+        objects.ClusterPluginLinkCollection.delete_by_cluster_id(
+            self.cluster.id)
+
         db().commit()
 
         supertask = Task(

nailgun/nailgun/test/integration/test_reset_environment.py

@@ -85,6 +85,41 @@ class TestResetEnvironment(BaseIntegrationTest):
             1
         )
 
+    @fake_tasks(
+        override_state={"progress": 100, "status": "ready"},
+        recover_nodes=False,
+        ia_nodes_count=1
+    )
+    def test_environment_reset_cleans_up_plugin_links(self):
+        cluster_db = self.env.create(
+            cluster_kwargs={},
+            nodes_kwargs=[
+                {"name": "First",
+                 "pending_addition": True},
+                {"name": "Second",
+                 "roles": ["compute"],
+                 "pending_addition": True}
+            ]
+        )
+        self.app.post(
+            reverse('ClusterPluginLinkCollectionHandler',
+                    kwargs={'cluster_id': cluster_db.id}),
+            jsonutils.dumps({
+                'title': 'simple link',
+                'description': 'simple description',
+                'url': 'http://example.com',
+            }),
+            headers=self.default_headers
+        )
+        self.env.launch_deployment()
+        self.env.reset_environment()
+        response = self.app.get(
+            reverse('ClusterPluginLinkCollectionHandler',
+                    kwargs={'cluster_id': cluster_db.id}),
+            headers=self.default_headers)
+        self.assertEqual(response.status_int, 200)
+        self.assertEqual(response.json, [])
+
     @fake_tasks(
         override_state={"progress": 100, "status": "ready"},
         recover_nodes=False,