Bug 1436369 Move buildbot periodic file updates to clearer name r=callek

Summary:
We'll be adding the new periodic file updates task to run in parallel. This patch
moves the existing one to make it clear it's running on buildbot, so we don't get confused
later on.

Reviewers: Callek

Reviewed By: Callek

Bug #: 1436369

Differential Revision: https://phabricator.services.mozilla.com/D681

--HG--
rename : taskcluster/ci/repo-update/kind.yml => taskcluster/ci/repo-update-bb/kind.yml
extra : rebase_source : c1386a05c378589efdd508199d97cb8121308686

taskcluster/taskgraph/target_tasks.py

@@ -621,5 +621,5 @@ def target_tasks_file_update(full_task_graph, parameters, graph_config):
     """
     def filter(task):
         # For now any task in the repo-update kind is ok
-        return task.kind in ['repo-update']
+        return task.kind in ['repo-update-bb']
     return [l for l, t in full_task_graph.tasks.iteritems() if filter(t)]