Ignore skipped groups (from AD)

As we can't tell whether they would have passed or failed, we should consider
them as if they didn't run (indeed, they didn't).

First step for #166

mozci/queries/push_tasks_results_from_unittest.query

@@ -8,6 +8,7 @@ where:
     and:
         - prefix: {repo.changeset.id: {$eval: rev}}
         - eq: {repo.branch.name: {$eval: branch}}
+        - ne: {result.status: "SKIP"}
         - ne: {treeherder.tier: 3}
         - ne: {task.kind: "decision-task"}
 limit: 10000

tests/test_task.py

@@ -69,7 +69,6 @@ def test_to_json():
     kwargs = {
         "id": 1,
         "label": "foobar",
-        "kind": "test",
         "result": "pass",
         "duration": 100,
     }